Martyn Waghorn left on crutches after Rangers cup victory

Rangers' Martyn Waghorn injured his knee shortly after scoring the opening goal. Picture: SNS

The English striker scored his 28th goal of the season with a third-minute penalty opener in the 2-1 fifth round replay win over Kilmarnock in Ayrshire.

But he limped off shortly afterwards, having damaged his right knee. The full extent of the injury will be assessed today but the prospect of losing the services of their prolific top scorer is an obvious concern for Rangers.

“He locked his legs, I don’t know if he got caught on the surface,” said manager Mark Warburton. “He scored the penalty, credit to him, but we will have to wait and see how he is. He is on crutches now and we will see how he is in the morning.”

Nicky Clark, who replaced Waghorn, scored a dramatic winner for Rangers in the second minute of stoppage time, with Kilmarnock having equalised through Rory McKenzie.

The win earned Rangers a home quarter-final against the winners of next week’s replay between Dundee and Dumbarton.

Warburton was satisfied by his team’s eventual dominance of last night’s match after an opening spell which was too frantic for his tastes. “We didn’t want to get involved in a cup fight,” he added. “We didn’t want a battle but the first 25 minutes were a battle. The last 15 of the first half were better, then in the second half we were very good.

“We wanted to control it and create chances, play it out from the back and I was really pleased with how we did that. It was a tremendous winning goal from Nicky but before that we had shots blocked and what I thought was a blatant penalty when Kenny Miller was fouled.

“We attacked, looked after the ball, were first to the ball with good energy. I felt we should have won the first game at Ibrox but we had a fantastic away support tonight and for the players to get their rewards in front of those fans was pleasing. It was a tough game at a tough venue but over the two games, I think most people would agree we were the stronger team and deserved to go through.

“We’ve got a home game in the quarter-finals now and we hope to have a full house at Ibrox which has been good for us this season.”

It was a painful evening for Kilmarnock who also dropped back into the Premiership relegation play-off place as a consequence of Motherwell’s 3-0 win at Dundee United.

But assistant manager Lee McCulloch, in charge of the team for the final time before new boss Lee Clark assumes full control this weekend, said: “The new gaffer came in before the game and also spoke to the lads at half-time. There was a lot out there tonight which would have encouraged him.”