Lesson learned I hope

My son threw against the team whose coach has helped him a little. In the past I could tell his arm was wrong in games I am sure from nerves. He has only thrown 3 times for a total of 6 innings. Anyway after the game the coach tells me he was not getting his fingers on top of the ball which is something he has preached to him about doing and we thought was fixed. He said about 1 of 10 he threw right and every time a nasty sinker type ball for a strike. Was telling my son what he said and then it dawned on him. Between innings he walked by him and held his arms out to equal/opposite and rotated his hand back but my son didn’t realize what he was talking about. I bet he will not make that throwing mistake again. It was the worst he has thrown but I think one of the best lessons learned so far. We play them again in 2 weeks and I hope he shows a little more of what he has that night!!!