Niskanen, who played with Crosby on the Penguins for four seasons before signing with the Capitals as an unrestricted free agent in 2014, said he did not mean to crosscheck him in the head.
"Absolutely not. It wasn't intentional," he said. "I've seen the replay. In super slow-mo, it looks really bad. I caught him high. I think he's coming across trying to score. As he's doing that, he's getting lower and lower, and when it's happening that fast, my stick and his head collided. I wasn't extending trying to hit him in the head. It happened quickly."
Niskanen said the point of contact was higher than intended because Crosby was falling.
"I wasn't even trying to crosscheck him with a serious amount of force," he said. "A collision was going to happen there in the crease. When the play first starts, I think my stick's at about his arm level probably, right about where the numbers are on the side of his jersey. And because he's trying to make a play, he's getting lower and lower because he's getting pressure trying to score."
Penguins forward Chris Kunitz saw the play differently.
"It's obviously gut-wrenching," Kunitz said. "A guy that is the best player in the world playing in his prime, just dominating games, it's one of those things that you look at it once and you see what actually happened and I think the next thing is watching how deliberate it was when the guy crosschecks him in the face.
"I thought all of that was kind of out of this League, but I guess not."
Capitals coach Barry Trotz called the hit a hockey play.
"If you look at it, Sid's coming across and [Capitals goaltender Braden Holtby] throws his stick out there," Trotz said "He sort of gets split and he's coming down and [Niskanen] has to go to the back post because that's where the puck's going and he just sort of ran into him. Unfortunately, Sid got injured there, but I don't know if in that situation you want the guy to throw his hands over his head. It's just hockey and it's a hockey play."