KRIS COMMONS has been a pain in the rear for many of Celtic's rivals over the years, but a strained gluteal muscle is making him an injury doubt for Thursday night's Europa League tie against Dinamo Zagreb.

The 31-year-old, last year's PFA Scotland and football writers' player of the year, was omitted from the match day squad for the Parkhead side's 2-1 Premiership win at St Mirren Park along with central defender Jason Denayer, who has been battling an ankle injury.

Manager Ronny Deila would say last night only that he was cautiously optimistic that both men would be available to face the Croatian champions.

Deila was also gloomy last night about long-term injury doubts, Mikael Lustig, Adam Matthews, James Forrest, and Charlie Mulgrew, returning in time for the game.

"It's hard to say how much we missed Kris, but he has a huge impact on the team," said Deila. "He has pulled a muscle in his butt. I hope he's back for Thursday - Jason as well. But I just don't know."

John Guidetti, who scored one and forced a Jim Goodwin own goal in Paisley, also picked up a minor muscle strain, but is ineligible to compete in European competition anyway. His performance, however, helped Celtic to their second win in four days, a result that was greeted with both relief and a measure of scorn by their Norwegian manager.

"It was a tough game," he said. "It was important we got back after the equaliser to win the game, which was a positive, and keeping their chances down was a positive. But we looked tired.

"We were always a metre behind in the challenges and we didn't win the second balls. And on the ball we were too slow. We didn't create so many chances either. So inside I feel a little bit irritated. But I also know it's tough to play three games and win on a day like this and some days it's just all about hard work and getting the result."