CRAIG Gordon ranks alongside Henrik Larsson and Lubo Moravcik as one of the greatest signings in Celtic's recent history, according to John Collins.

The goalkeeper is likely to be a key man for Celtic when they take on Inter Milan in the last 32 of the Europa League tomorrow night and Collins described him as an "unbelievable" piece of business by the club. Celtic conceded 11 goals in their successful group campaign but Gordon was consistently excellent against Red Bull Salzburg, Dinamo Zagreb and Astra Giurgiu.

The 32-year-old arrived as a free agent in the summer after doubts about whether he would ever play again. A knee injury at Sunderland meant he did not play a senior game for two years from April, 2012. Instead he has been exceptional, arguably surpassing the performances of his predecessor, Fraser Forster, and even earning a Scotland international recall against England in November.

"We're just so fortunate," said Collins. "He's been an unbelievable signing, what a deal it was." Larsson joined Celtic for £650,000 in 1997 and Moravcik arrived for £300,000 the following year, and Collins was asked if he could be compared to that iconic pair. "He'll be up there, he's got to be spoken about in the same bracket as those two.

"Where does he rate in Europe? All I will say is that he's class, pure class. He's a great example to all the players about how he goes about his business. We knew Craig was good but when you have been out for two years you think he'll never be the same again. But I think he's better now than when I remember him from before the injuries. That's incredible. Goalkeepers get better with age and mature."

Celtic had been apprehensive about committing to Gordon because of the length of time he had been out of the game. "Anyone that says otherwise is telling lies. If you haven't played for such a long time in such a key position then there's a doubt. But it's been great news for us. We certainly never thought he was finished but Steve Woods has to take all the credit. He brought him to the club and assessed him and gave us the green light by saying that he believed in Craig. Our goalkeeping coach has to take all the credit.

"From the first minute he walked in the door and I met him you could tell he was the complete professional and in total control of his emotions. From the first game he played he was never flustered and always calm. He makes things look easy which is always the sign of a good player. He transfers that calmness onto his defenders."

Kris Commons is almost certainly out of the first leg because of a hamstring strain. He trained at Lennoxtown yesterday but could not complete a full session. Celtic will not involve him if there is any chance of aggravating the problem and his only chance of playing at all is as a substitute.