Brad mentioned this last night in his wrap-up of the game, but I figure I'd add a video for those of us who missed it.
Tarasenko was near the boards in his own end and was backhanding the puck back to a teammate. He was facing down the ice, but was turned, looking over his shoulder. Coming from his front side, Olver laid a hard...mostly clean hit on the rookie Russian. Tarasenko never saw him, got knocked flat backwards and possibly hit his head on the ice. When he rolled over, cameras caught a dazed look on his face, his eyes rolling back in his head. He was spitting out blood. It took a minute for him to gather himself and then he was helped back to the dressing room, at first to address the blood in his mouth and then probably to assess a possible concussion.
On the slow-motion replay, it looked like Olver's shoulder hit Tarasenko in the head. Front row Blues fans behind an arguing Ken Hitchcock were pointing their elbows. While Olver raise his hand on the hit, he didn't stick his elbow out. It doesn't mean that the the next time the Blues and Avalanche play that Olver won't have to answer for the hit. He probably will. That's how these things work. But it's not like the guy will be suspended or fined.
Of course Tarasenko didn't return to the game.We'll say it: He's day to day with an upper body injury.
Well, of course not. Because what would a shortened season be without the Blues getting a key player back, and then losing another one? Got to keep stuff balanced, no? SB Nation's NHL hub has a better view of the whole thing through a .gif, and it does not look good.
It looks like he led in with his shoulder, and as Tarasenko turned, he got the full force right in his face. The trick here is figuring out if Olver had enough time to realize that Tarasenko was turning. Also, would Olver have even stopped? He's not exactly a penalty machine and doesn't have a reputation for being a dirty player, so this looks like an unfortunate accident more than anything else.
Regardless of if it was an accident, Director of Player Safety Brendan Shanahan will probably take a glance at it. There was no penalty on the play, but that doesn't mean anything as far as discipline.
EDIT: From TSN's Bob MacKenzie:
Mark Olver's hit on Vladimir Tarasenko in last night's COL-STL game has been deemed legal hit and no further action is being contemplated.— Bob McKenzie (@TSNBobMcKenzie) February 21, 2013