Gene Hackman did not receive an Oscar nomination for portraying Norman Dale in Hoosiers.
Hackman firstly just is very believably in the role as a man who clearly not exactly currently in the best part of his life. Dale's coaching job after all is more of a last ditch chance at redemption more than his ideal choice of work. Hackman wears some of that bitterness in him quite well. It is not something that Hackman let's overwhelm his performance, but he does well to suggest the past without the film really needing to show it. Most of the film is not dwelling on the past instead obviously focusing on Dale's attempt to try to get the small town team in shape to win the championship well carefully dealing with the locals who basically want to replace him as soon as they see him. Again in performing as the coach Hackman again does not act as the usual type of movie coach.
In the coaching duties Hackman delivers with a fervent passion as well as always a certain intelligence in his ways as a mentor. What makes Hackman so effective though is the way he comes off as a particularly realistic coach especially in the game scenes. Hackman portrays Dale as honestly having a pretty bad temper in the game, and does not hold back in that regard. Hackman is always particularly strong in showing that Dale does not take it well when anyone whether it is the game's referee or one of his players, he someone who knows he's right so he's not going to take that from anyone. Hackman does not show that Dale is really a perfect guy who someone you would even want to be around, but because of that he's always particularly believable in this role.
That is not to say that Norman Dale is not an inspiring figure in the film, quite the contrary not only does he pull all the boys together to form an actual team he even gets the local drunkard (Dennis Hopper) to redeem himself slightly by becoming an assistant coach for the team. Hackman again is terrific by not going the standard route by being particularly warm and lovey dovey. Instead in most of these scenes Hackman is very careful to suggest an underlying empathy in Dale as he tries to give his inspirational speeches, but the way Hackman plays it up front is as basically "Do the right thing, or well I just down give a damn". Hackman completely meets the challenge of being the inspiring coach, but he always does it his way which avoids ever falling into the slightest bit of schmaltz.
Gene Hackman being in the lead role helps Hoosiers stand out as sports movies of this kind. He does not hit the usual beats of this type of character instead taking his own path the whole way through. By doing this Hacman not only gives a much more intense and compelling portrayal, but also one far more line with a real coach in Norman Dale's position. He makes him a pretty rough character and one that is not always easy to deal with, but Hackman never fails to perfectly balance those technically less savory qualities with a great deal of genuine heart and passion. Although I would not quite put this up there with Hackman's best performances, it is a great example of Hackman excelling in yet another genre.