Other mistake: In Roy Hobbs' last at bat of the movie he takes the 1st pitch for a called strike (confirmed by closed captioning). The 2nd pitch is called a ball. The Pittsburgh manager then decides to change pitchers with the count at 1-1. The relief pitcher's 1st pitch is fouled into the press box making the count 1 ball and 2 strikes. The 2nd pitch from the relief pitcher is swung on and missed, and should be strike 3. Hobbs stays in the box and hits a long fly ball foul and hits a HR on the next pitch. Roy Hobbs should have struck out. (02:06:20 - 02:12:05)
Continuity mistake: When he hits the ball off the clock, everyone leaves the park after his home run. Why should they? Roy Hobbs' team is the visiting team, so the Chicago Cubs still have their turn at bat in the bottom of the ninth.