Rangers suffered a potential injury blow as Martyn Waghorn was substituted early against Kilmarnock.
Waghorn had scored the opening goal from the penalty spot in the 2-1 Scottish Cup win, adding to his prolific goal tally for the season.
He actually injured himself in the lead up the penalty as he won it, knocking his knee, and left the stadium on crutches.
Rangers boss Mark Warburton spoke after the game and explained he hoped the crutches were just as a precaution, but Waghorn would have to be assessed.
Quoted by Eurosport, Warburton said: "With Martyn it was one of those ones where he locked legs as he fell. I don't know if he caught the surface or not but he has an abrasion on his knee.
"He took the penalty, credit to him, but we will see how he is. He is on crutches and we will see how he is in the morning."
Rangers are into the quarter final as a result of the victory, thanks to Nicky Clark scoring a stoppage time winner to send the Gers through.
Waghorn, 26, now has 28 goals for the season in all competitions, and Rangers would not want to be without him for a substantial period of time.
They have an eight point lead at the top of the Scottish Championship, although second place Hibernian have a game in hand.
Here is a look at how Rangers fans reacted on Twitter to Waghorn's injury...
Waghorn left stadium on crutches, hopefully a precaution. Thankfully we got King and O'Halloran in. Crucial we got more forwards in January.— Smit (@TheBigBlueBear6) February 16, 2016
Only Martyn Waghorn could get injured but score the penalty before being subbed off #hardcore— Herrenvolk Loyal (@StaunchusPilate) February 16, 2016
Waghorn on crutches leaving rugby park, my bet for him being top scorer in Europe is beat then— michael mcdonnell (@mick6790) February 16, 2016
If Waghorn's injury is a bad one it just highlights that we really should have signed a striker in the transfer window— Will Robbo (@wullieboy78) February 16, 2016