As Newcastle United have three matches left to qualify for a place in a European competition, this would set the time of the story towards the end of April (mid spring). However the climatic conditions depicted show what North East England is like in winter.
When Santiago is kicking balls into dumpsters in a back alley, he's clearly right footed. However the free-kick he scores against Liverpool at the end of the film is taken by a left footer (Laurent Robert).
Right before the last game, Santiago practices free shots in the stadium. When Dornhelm calls his name, he proceeds to kick what appears to be the last ball remaining. However as Santi is shown kicking the "last ball", the shot changes to him kicking one of the many balls that are aligned next to him. When the scene changes back to Santiago walking toward Dornhelm, the balls are gone.
When Santiago and Glen are traveling over the Tyne Bridge on their way for what is Santiago's first sight of the stadium, they clearly leave the bridge and Glen says 'There it is'. Then it immediately cuts to a shot of St.James' park which in actual fact is a fair few miles away from the Bridge itself. It is a noticeable error as we can see from outside Santiago's window an office block which is evidently built at the entrance to the Tyne Bridge.
When Newcastle play Man Utd in a reserve team game, "THE BEES" can be seen spelled out in white seats in one of the stands. The Bees is the nickname of Brentford Football Club and they are located west of London. Neither Newcastle or Man Utd would play reserve games there.
When Santiago arrives in Newcastle on the train it is seen entering Newcastle from the manors end of Newcastle which is on the Edinburgh line if he was to come from London as in the film he would have came the other direction, The same can be seen when it enters the station the train is first class at the front meaning it is southbound train not northbound.
When Santiago goes for a run across the Tyne Bridge, he runs off in the direction of Gateshead, on the south bank of the river. However, it is portrayed that he runs off the bridge and onto the beach, which is Tynemouth Longsands, being on the north side of the river about 10 miles away.
In the story Newcastle have 3 matches left and since they're trying to qualify for a place in a European competition, logically it is the end of the season. Yet, we see that Newcastle sign Gavin Harris around the same time (so that they could win the remaining matches) which is impossible because a club can only sign a player in the summer or winter break. They can sign a player during the season but he would not be eligible to play for the new club.
To play in the English Premiership, if you are from outside the EU, you have to have a work permit. You automatically qualify for one if you have played in 75% of your national teams matches in the past year. Otherwise, you have to go to a tribunal where it has to be shown that you are an outstanding talent that is worthy of a permit. Since he had to basically beg for a trial, it would be highly unlikely that he would win a decision in a tribunal.