St Mirren are set to be without Australia international Ryan Strain for three months.

The wing-back is due to undergo surgery on the groin injury he suffered on international duty last month.

Manager Stephen Robinson said: “Ryan has gone to London for surgery. He will have surgery on Monday and unfortunately he will be in the region of three months, which is a huge blow for us.

“But it’s up to other people to step into the plate now. We have a small squad which is tested to the limit with injuries, especially long-term ones, but we are no different to anyone else.

“I don’t work on the excuse mentality, I try and work on the basis that someone else will get an opportunity to prove they should be in the side and make up for Ryan’s loss.”

The 26-year-old is approaching a crucial time in his career with his contract due to expire at the end of the season.

Robinson said: “We spoke with Ryan’s representatives about a new contract and they weren’t interested at that stage in terms of signing.

“Ryan has obviously had a huge blow with his injury and it’s a blow to us because Ryan has been a big, integral part of what we have done in our relative success.

“But you can’t feel sorry for yourself. Ryan will get the best medical treatment possible and he’s got the best physio around that will help him get back.

“He has to buy into that, he has to have the attitude and the work ethic that Jonah Ayunga had with a long-term injury.

“His aim as a young man is to come back stronger and fitter than he was before.

“Then the decision is in his hands in terms of what he does the following season but hopefully he will be back long before then.”

Saints take on Rangers at Ibrox on Sunday and Robinson is optimistic they will show more belief than they did in Tuesday’s 1-0 defeat against Ross County, who scored late on through Jordan White.

“You need belief,” Robinson said. “We have got the talent.

“Our lessons from Tuesday night, my biggest frustration wasn’t actually losing the game. If we had drawn the game I would still have been frustrated with our performance because we didn’t put our stamp on the game, our style on the game.

“That has to be what we do at Ibrox, we have a belief that, when we land on the ball, we can play.

“We believe we have players who can hurt Rangers in certain areas and we will go there with a belief.

“We learn our lessons, you have ups and downs. It’s never going to be smooth journey as a football manager or a football squad but we have a group of players who totally believe in each other.

“We looked like we didn’t have a little bit of belief for certain periods but we have spoken about it and I’m sure will be better for it.”

Stephen Robinson fears Ryan Strain could be out for weeks with a groin strain as he welcomed back fit-again Jonah Ayunga to his St Mirren squad.

The 26-year-old wing-back had to go off in the first half of Australia’s World Cup qualifier against Palestine in Kuwait and had a scan on his injury on returning to Scotland.

Ayunga has not played for the Buddies since he ruptured his ACL against Motherwell in January, but the 26-year-old striker has worked himself back into contention for the cinch Premiership game against Livingston on Saturday.

The St Mirren boss is looking for a “reset” after a 4-0 defeat by Dundee before the international break, but will also have Keanu Baccus suspended for the visit of the Lions to Paisley.

Robinson said: “Ryan Strain came back with a groin injury, which we had scanned yesterday, so we are still waiting on results from it but we are not very hopeful.

“He certainly won’t be available for Saturday. It looks like it will be weeks rather than days so it is a big blow for us.

“Jonah has been training for nearly six weeks now which is a lot of good training time.

“He played 90 minutes last week (bounce game) and was very good. So he is certainly ready to be involved, at what stage or level we will decide in the next 24 hours.

“Jonah is a very laid back boy. There is not a lot that gets him up or down. I am sure there is maybe a different side to him at home, but he is a great boy, a boy who I have worked with at two clubs.

“He has pushed himself and credit must go to Gerry Docherty (physio) and Gary McColl (strength and conditioning), who have pushed him to the limit and got him into a condition that he is ready to go. It is credit to all three.

“I felt the game against Dundee was a one-off game, where as a collective we didn’t play particularly well and we need to reset ourselves again and do what we were doing which was not playing in front of people and I am comfortable we will do that on Saturday. We want to get another win under our belt.”