He didn't land a solid punch and Bryce should consider himself lucky. I he had, it probably breaks his hand
Why would your hand break if you land a solid punch? Strickland landed what amounted to a slap and Harper's counter was too loopy to land with any authority. Harper was close enough to where he could've stunned Strickland if his punch had been straight.
I'm inclined to believe he was throwing the helmet at Strickland and it slipped out of his hand.
He was definitely trying to throw his helmet at Strickland but it slipped. All in all, the fight was better than what we usually see in baseball. Harper elevated himself in my estimation with what he did today. You can't allow someone to throw at you like that without striking back (and there's no doubt in my mind Strickland did it on purpose).