In the first period of his NHL debut, Grebenkin crushed Vegas Golden Knights defenseman Shea Theodore from behind in a hit that left the veteran defenseman bloodied.
Surprisingly, no penalty was called on the play and as Jesse Granger of The Athletic reported, the Maple Leafs almost scored had Adin Hill not made a big save on Nicholas Robertson with 36 seconds remaining in the period.
Theodore turned his back with Grebenkin approaching him and the rookie delivered a hard hit that left the defender in a very tough position. His head hit the boards straight-on and left him bloodied from his forehead.
It remains to be seen if the NHL's Department of Player Safety will get involved, especially with no penalty called on the initial play, however these are the hits they're trying to crack down on.
Ryan Reaves was already handed a 5-game suspension for his check to the head on Edmonton Oilers' defenseman Darnell Nurse and will be out of the lineup for 4 more games.
Grebenkin's hit on Theodore wasn't the only questionable hit in this one, as Zach Whitecloud may also face potential supplemental discipline for his brutal hit on Matthew Knies in the second period.
Grebenkin was called up alongside fellow rookie Fraser Minten, who scored his first career NHL goal in the 3-0 win.