Rangers striker Martyn Waghorn aiming to find his form in time for Celtic

Rangers striker Martyn Waghorn admits he has not felt like his old self this season - but hopes to perk himself up by shooting down Celtic.

Gers' top-scorer from last term spent four weeks out of action after pulling his hamstring on the opening day of the campaign against Hamilton.

And he has struggled to rediscover his lethal touch since returning last month.

His only Ladbrokes Premiership strike of the season so far came just minutes before he hobbled off against Accies and although he did net a hat-trick against Queen of the South in the BetFred Cup quarter-finals, his treble failed to spark him back into form.

The Light Blues now face Celtic at Hampden in Sunday's last-four showdown and Waghorn reckons it is the perfect time to end his three-game scoring drought.

He said: "I started the season feeling really good but the injury affected me in terms of stopping me from kicking on and getting going.

"These past few weeks I still think I've been off the pace a little bit. I've not been my usual self in terms of being a threat up front.

"The longer the run goes without scoring the more you end up snatching at things. You don't mean to do it purposely but I put a lot of pressure on myself to perform. I want to score goals and play well.

"I've been working hard this week though. I've realised what I need to work on.

"I'm still learning. It's been a step up to the Premiership and as a group we are still developing. I know personally I can do better and I'm working on that. Hopefully I can kick on this weekend."

Waghorn's strike partner Kenny Miller knows just what these derby battles are all about.

Sunday's encounter will be his 20th over three spells with Rangers and his one-year stint at Parkhead.

But having crossed the divide twice, the veteran former Scotland frontman has not always had it easy and was this week the subject of a viral video showing him being targeted for abuse by a Hoops supporter whilst out shopping.

Waghorn, though, thought his team-mate handled the incident with the same poise he shows to opposition defenders.

He said: "That's the sort of thing you have to deal with. It's not great, it's not ideal. It's childish but it's one of those things that some people are going to do to try and get under your skin.

"He handled it very well and walked away. That's all you can do in those circumstances.

"Kenny has been absolutely brilliant. Since the day I came in here he has helped and guided me so I know what it's like to play for Rangers and how to deal with all the pressures.

"It was absolutely fantastic that he got his 100th goal against Inverness last weekend and I'm so pleased for him.

"He's one of the fittest 36-year-olds you'll ever meet. The way he trains, the way he works is impressive. He's on it 100 per cent every day."

Rangers have suffered a major injury blow with playmaker Niko Kranjcar struck down with a serious knee injury, Press Association Sport understands.

The Croatian could be sidelined for months to come if the injury is as bad as Gers chiefs fear.

Former Portsmouth and Tottenham midfielder Kranjcar damaged knee ligaments in a freak training ground accident on Tuesday.

Ibrox medics are now waiting for the swelling to go down before they are able to fully assess the problem but he could be ruled out for six months or more if the issue turns out to be a ruptured cruciate ligament.

His loss is a huge setback for Light Blues boss Mark Warburton, who has been seeing more from the 32-year-old in recent weeks after a sluggish start to his Glasgow switch.