Nunez missed a sitter to win the game at the end, leaving Fowler unimpressed.
He said on TNT Sports: "People worry about Darwin Nunez... he doesn't think about the game enough.
"If you're struggling for confidence, you've got to go back to basics, you've got to get the ball, you've got to touch it and you've got to give it five yards.
"You don't look and dally on the ball waiting for someone to make the run so you can play an unbelievable pass, play the simple things.
"You always need to go back to basics and do the simplicity of being a footballer, what got you into the position of being a professional footballer.
"It's a bad miss, it's a really bad miss, probably up there with one of the worst we've seen this year.
"I'll try and help him out a little bit by saying, '(Dominik) Szoboszlai maybe should've shot himself'.
"But, he's played a great ball to him and he's missed the target, criminally from seven, eight yards. That can't be happening."