Crosby, who's more known for his skills than his fighting, didn't like the hit on Letang and decided to settle the score by throwing punches. The two players exchanged blows in a scrappy fight, with no clear winner.
In the end, Crosby managed to bring Krebs down to the ice, ending the fight. This isn't something you see from Crosby often, but it shows his determination to stand up for his teammates, even in preseason games.