In the scene where Rick Vaughn pitches for the first time during spring training, the "NO PEPPER" sign is on the left side of home plate before Vaughn pitches. After Vaughn throws his pitch, the sign moves to a location directly above home plate which is where the ball shatters the sign.
When Lou Brown talks to Vaughn about sending him back to the minors to work on his control, he says "take Ryan there," motioning to a picture behind him as an example of a pitcher who turned it around in the minors. Yet "Ryan" is clearly dubbed; Brown mouths "Koufax" and indeed you can see a picture of the left-handed Sandy Koufax when Brown stands up. This line was likely changed after someone informed the writer/director David S. Ward that Sandy Koufax never played a day in the minor leagues, joining the Dodgers right out of high school.
In the Indians locker room prior to the opening game, Ricky Vaughn is sitting in a chair and nervously flipping and catching a baseball into the air with one hand. Jake Taylor comes over and says, "Relax kid, we've got 161 of these games left to go." On the next flip, Vaughn is supposed to be rattled by Taylor's comment and miss the catch (evidenced by the audible "thud" of the ball on the floor). However, if you look at the bottom of the frame, you can actually see Vaughn still catch the ball in his hand.
In his final at-bat Jake (the catcher) has a close up of his hands with the bat on his shoulder. His knuckles are aligned incorrectly. All real baseball players know that the "knocking knuckles" must be aligned while the bat is on your shoulder in order to have straight wrists when following through with your swing. (this error happens several times during the movie from other characters). If you don't align your "knocking knuckles" correctly, one or both of your wrists will be bent and you will have difficulty swinging with power.
When Dorn throws out a Yankee to end the top of the first inning in the final game Harry Doyle (Bob Uecker) says that he threw over to "Metcalf" but the first baseman's name was Ward, as that was what was on the back of his jersey.
In the final "bunt and steal" scene, after the signs have been given by Lou Brown and the base coach, Taylor is knocked down by an up and in fastball by the Duke. Hayes should have been running on the pitch as he would have assumed Taylor was bunting based on the signs. There's no way the signal would have included a "run on the 2nd pitch" instruction as Taylor already had one strike on him. Hayes steals on the next pitch and scores on Taylor's bunt single.
When Dorn (#24) gets his hit in the 7th inning of the playoff game, the shot of the base runner rounding first base shows his number as #8, and the first base coach has #2. When his face is shown again, Dorn's number is back to #24, and the first base coach is shown to be wearing #16 in all other shots.
In Jake's last at-bat, the Yankee pitcher throws him a brush-back pitch which causes him to dive into the dirt to avoid being hit. While on the ground, his uniform is very dirty from the dust of the batter's box. The Indian's radio announcer (Bob Uecker) says that "Taylor refuses to dust himself off". However, as Jake re-takes his stance, his uniform is clean. As Jake crosses first base on his bunt attempt, he falls into the dirt of the base path, again becoming very soiled. But in the post-game scenes he again has a clean, spiffy uniform.
In the final game, during Haywood's last at bat, Jake Taylor (the catcher) is nearly standing for the final "strike-out" pitch by Vaughn. First, a catcher would never stand that tall, unless they were making the pitch an obvious high, out-of-the-strike-zone pitch. Second, as Haywood swings through the pitch for Strike 3, the ball is shown hitting Jake Taylor's catcher's mitt perfectly in the middle of the strike zone, about a foot below where the ball was just one frame earlier. Incorrect. Catchers definitely stand that tall, although it is not common. Vaughn hit the glove, but hit it at the high target set by Taylor. There is nothing in the film that suggests the pitch was in the strike zone.
At the end of the movie, right after Willie Mays Hayes has been called safe at home, he jumps up and runs out to Jake Taylor, and as they celebrate, his batting helmet disappears and reappears between shots.
When the Indians are playing Oakland in the "national television" game and Mike Rexman (Oakland), is at the plate the sun angle changes drastically between when Jake goes out to talk to Rick Vaughn and the last pitch of the game.
In the top of the 9th during the one game playoff against the Yankees, the stadium clock reads 10:20 PM as Vaughn is coming in from the bullpen. In the bottom of the 9th right as the Duke comes in from the bullpen, the stadium clock still reads 10:20 PM.
In the final game against the Yanks, the # 37 player is hitting, Jake Taylor then throws to 1st base to pick off the #37 player. The #37 player appears later in the game, this time being referred to by a different name by Harry Doyle.
During spring training, after the game against the Cubs, when players are looking to see if they got cut, Cerrano takes the snake and rubs the face of it on the paint on the locker. There is already a circle painted on the locker, and Cerrano makes a cross inside the circle with the snake. When the camera changes views, there is no cross on his locker.
In the final scene of the film, at the point where Jake is holding Lynn up and Vaughn and Willie exchange their special handshake, you can see that Willie's jersey is much cleaner than it was while running the bases in the process of scoring the winning run.
Just after all the players report to spring training, there is a shot of Roger Dorn walking with his duffel bag over his shoulder in the room with all the bunk beds. Right behind him, an extra playing one of the baseball player hopefuls (he has a mustache and is carrying a bag also) is walking behind him. The scene cuts to Dorn saying hello to Jake Taylor (Tom Berenger). When it cuts back to just Dorn, you can see that same extra doing exactly the same walking pattern he just did a second ago, like he just arrived twice.
When Dorn throws out the runner at first, the throw is caught by a right handed first baseman. When the Indians run off the field, it is an entirely different group of players. The 1B is now left-handed and wearing Dorn's #24, the pitcher is much younger looking and wearing #10.
When Lou has Ricky Vaughn in his office and is discussing his eyesight problem, there are a pair of glasses sitting on top of Lou's desk. Lou writes down some letters on a pad, the camera angle changes as Lou stands up; the glasses are no longer on the desk.
For Serano's home run in the playoff game with the Yankees - in a portion of the shots the bat is perfectly clean and shiny and the next second it is dirty and does not look as though it has ever been cleaned.
After the Indians start winning and have a record that is roughly 60-61, a series of newspaper articles sequentially appears with news of the Indians' latest success. The dates on the newspapers are inconsistent. The first one is some time in May (you can't have played 121 games by May!). Then as the season progresses and the Indians move toward first place, the newspaper dates move backwards into April, again an impossibility.
While the Yankees are batting in the top of the 9th in the playoff game, the scoreboard shows a 0 for runs in the inning for NY. After Haywood's strikeout ends the inning, they cut to a closeup of the scoreboard putting up the 0.
When they report to spring training in the bunk room Willie introduces himself to Jake and Ricky, seconds later Cerrano takes Dorn's golf club cover to use for his bat and in the background you see Willie just walking through the door. But that would be impossible since Willie was just talking to Jake and Ricky seconds before.
The stadium that the Cleveland Indians play their home games in throughout the movie is actually the old Milwaukee County Stadium, former home of the Milwaukee Brewers. Some billboards/ads in the stadium were not removed, like advertisements for area radio stations 94 WKTI and 620 WTMJ.
After Harris gives up the walk in the top of the 9th inning, the scoreboard shows 7 hits for the Yanks. Vaughn comes in and gets a strikeout. After Hayes gets a hit in the bottom of the 9th, the scoreboard shows 9 hits for the Yanks when, in fact, they only have 7.
As Cerrano hits his game tying home run in the playoff game against the Yankees, he is seen running the bases with the bat in his hand, which (then and now) is an eject-able offense in Major League Baseball.
After Taylor grounds out in the 7th for 2 outs Dorn singles and Cerano homers. Taylor comes up in the ninth with 2 out and a man on. That implies 9 at bats since he grounded out. There are only 8 at bats between the same spot in the batting order. 7th inning single, homer and 3rd out of inning. 8th inning 3 outs and 9th inning 2 outs and a single. Either there should have been only one out or Dorn up with two outs.
When Jake first follows Lynn to her fiancé's apartment, he is able to just walk in, and go right in without needing a key, or be allowed in. Considering that it's most likely a high class building, Jake would have to break in.
In the last game against the Yankees, at "Two outs, top of the ninth, still tied at 2, Harris working on a 7-hitter" the local NBC station name is visible on the scoreboard over Harris' shoulder as WTMJ TV 4. WTMJ 4 is based out of Milwaukee. If it were Cleveland, it would read WKYC 3.
In the all-important bottom of the ninth inning, prior to Jake Taylor calling his shot, Willie Mays Hayes is at first. What probably is a hit-and-run play, Taylor swings and misses while Hayes is headed for second. As Hayes slides in to second you hear more than one person call "safe".
In the final-cutdown scene, the team is in their home clubhouse as evidenced by Cerrano's elaborate decoration of his locker, as well as the sign outside when Hayes celebrates. The team is wearing their (gray) road uniforms.
Willie Mays Hayes scores an infield single in his first at-bat of the season. However, the ball he puts in play hits Hayes' body right after his bat. Rule 6.05(h) states that this should have been ruled a foul ball.
In the ninth inning of the final game against the Yankees, Vaughn comes out to retire the last hitter. With the bases loaded, Jake (the catcher) only gives one set of signals. In such situations, there are two, sometimes even three sets of signals to prevent on base players from stealing signals and communicating to the batter what is coming.
In the bus, Lou Brown tells Vaughn that he is starting Harris in the Yankee game instead of him. Vaughn is clearly a starting pitcher and would thus not normally be in the bullpen for the final out of the game. However, it is not uncommon for all pitchers (including starters) to be available during winner-take-all games. For example, Randy Johnson pitched in relief for the Mariners and was the winning pitcher in Game 5 of the 1995 ALDS against the Yankees.
Cerrano and Haywood tossed their bats and their helmets to the ground, which (then and now) is believed to be an ejectable offense in Major League Baseball. However, this is only true when an umpire feels the player is "showing up the umpire." Any umpire would see this is in disgust of their own action and would never throw out a player for that.
When pitching, Vaughn is using an outfielder's glove which is somewhat bigger than a glove a "real" pitcher or infielder would use. However, many baseball players are highly superstitious and many pitchers do use non-infielder gloves, including at least one pitcher in the early 90s who used a catcher's mitt.
When the Indians start making their run and we start to see the newspaper articles, the first 3 headlines we see include the same article. It reads "Kansas City-" even though none of the first three games mentioned were against Kansas City. Furthermore, the article mentions Doug Jones, a real-life Indians reliever in the late-80's/early-'90s.
After Vaughn strikes out Haywood to end the top of the 9th inning, the Yankees first base coach is still seen in the 1st base coach's box as the Indians enter their dugout to begin the bottom of the 9th inning. In reality, the coach would have left the field right away.
During the first game, there are several shots of the stadium scoreboard with the clock indicating it is approximately 10:50AM. No regular season major league game would start that early in the morning.
The goof item below may give away important plot points.
In the one-game playoff with the Yankees, after Taylor bunts Willie Mays Hayes tries to score. When the catcher catches the ball thrown from first base you see the umpire behind him without his cap on in a shot filmed from behind first. In the next two shots with Hayes sliding and the umpire calling 'safe, safe' he is wearing his cap again.