Michigan head coach Jim Harbaugh has faced his fair share of criticism throughout his career, both as a player and as a coach. It’s just something that comes with the territory when you’re a major sports figure.

But there’s one thing that crosses the line when it comes to criticism that Harbaugh can’t stand: question an individual’s toughness.

Golf Channel analyst Brandel Chamblee criticized Brooks Koepka this weekend, saying he wasn’t sure if he was as mentally tough as some of the other golfers participating in the PGA Championship. Koepka, of course, hushed that critiqued after winning the event for a second-straight year.

But Koepka’s win didn’t keep Harbaugh from slamming Chamblee for his comments. The Michigan head coach fired off a tweet on Monday, bashing Chamblee for his criticism of Koepka.

After Chamblee caught plenty of flack for his comments, he sent out a tweet of his own to clarify the message.

After winning the tournament, Koepka said the comments from Chamblee “pissed me off” and that he used the criticism as fuel throughout the tournament.

It worked out pretty well for him.