Hi there! Grammatically it is good, it is an inverted form of the 3rd conditional. I would say this: 'Had his teammates not passed him the basketball, he couldn't have won the game for them.' I would use 'couldn't have' instead of 'could hardly have'. Hardly means that something is true to a certain extent. Here I would say if his teammates hadn't passed him the ball, there is zero chance he could have won the game, which would mean that it is not true at all, so 'hardly' wouldn't work. If you want to say that there was some chance that he could have won the game even if his teammates hadn't passed him the ball, it is much better to use may or might: 'Had his teammates not passed him the basketball, he may not have been able to win the game for them' I hope this helps, let me know if you have any questions!

His teammates didn't pass to him the ball, that's why (so that) he could hardly won the game.