The Edmonton Oilers forward slammed the 26-year-old defenceman face-first into the boards from behind during the third period of Friday's game.
Gagner was not penalized on the play. The Penguins defenceman seemed shaken up but did not leave the game.
Letang has already missed a significant chunk of this campaign seeing action in only 26 games. An elbow injury forced Letang out of Pittsburgh’s lineup for much of December and January.
Check out the video above to see what took place. Do you think Gagner should have been penalized? Do Gagner’s actions merit additional discipline?