In the final game when Miles is pitching, on his first pitch he starts his wind-up, then stops to wave his arms and dance to "Big Papa". After this he goes back into his wind-up and pitches. Since there was a runner on base. This would be a called a "dead ball" by the umpire, and the pitch would result in a ball.
In Duffy's bar, when Conor and Ticky are celebrating Conor's win, Conor and Duffy are talking, not only does Conor's beer grow in size between shots, but the man in the blue suit disappears and reappears.
After Conor places the $12,000 bet on what was supposed to be
a Chicago Bulls vs. Miami Heat NBA game, he and Ticky watch the game through the window of a sports bar. But the game footage is from a Continental Basketball Association (CBA) game played at the Sundome in Yakima, Washington.
Characters often discuss going to "Sluggers" (a sports bar) and refer to it as being "on the corner of Clark and Addison". "Sluggers" is a real sports bar and several scenes from the film were shot there, however it is not on the corner of Clark and Addison - another famous sports bar, "The Cubby Bear", is the only bar on that corner. "Sluggers" (3540 N. Clark Street) is actually a full block from the intersection of Clark and Addison and is located at the intersection of Clark and Eddy.
In the Kekumbas' first game, the home plate umpire incorrectly brushes off the plate by facing the infielders and squatting. When the home plate umpire brushes off home plate they are supposed to turn their back to the infielders and bend over.
In the "regotiation scene" with G-Baby, only G-Baby and Conor are in the dugout. It then cuts in showing the Kekambas batting. If this were the case, most of the team would be seated in the dugout. Since the dugout only had Conor and G-Baby in it, the rest of the team would be playing defense out in the field.
The goof item below may give away important plot points.
Incorrectly regarded as goofs
When G-Baby is shot, the bullet hole appears to be from a handgun bullet. He is behind all of the gangsters shooting with handguns and the only shots fired back are from a shotgun. However, a shotgun fires a shell that contains several BB pellets that spread in a pattern the further the target is away from the gun. G-Baby would have been hit by a single errant pellet, thereby causing the single hole that seems to be from a bullet.