A DAY after agitating about Rangers not having trophies taken away from them, Celtic took a giant step towards adding another of their own.

Their place in the semi-final of the William Hill Scottish Cup did not come easy, however. A dominant first-half performance gave way to more of a rearguard retreat after the interval, the sound of Celtic manager Neil Lennon beseeching his players to "keep it, keep it" at the corner flag in the closing stages telling its own story.

St Mirren caused one of the upsets of the season when they dumped Celtic from the Scottish Communities League Cup and they threatened a similar outcome here as they doggedly pursued the late equaliser that would have earned a replay.

The introduction of Graham Carey after 73 minutes was the catalyst for the late charge. Within minutes the Irishman, who scored a spectacular 30-yarder against Hearts earlier in the week, had sent Esmael Goncalves running through on goal with the most sumptuous of long-range passes, only for Fraser Forster to save the forward's shot. Then came Carey's big moment. The former Celtic prospect won a free kick around 25 yards from goal and sprung up quickly, eager to take it. His strike was destined for the far corner, but Forster was equal to it and made a fantastic reactive stop. The goalkeeper, in fact, was one of Celtic's key performers in the second half, having also denied Steven Thompson with a well-timed tackle as the pair raced on to a 50:50 ball outside the penalty box.

That this wasn't to be St Mirren's day became apparent in the final minute when a cross from the right was somehow missed by substitute Sam Parkin and Lee Mair at the back post could only fizz his shot wide. Mair said: "Two of their defenders were closing me down quickly so I just had to snap at it. Unfortunately, it hit the side netting."

Celtic had strong performers in Forster, Joe Ledley and James Forrest – who created both goals – but none put in more of a shift than their manager, who looked as if he might self-combust on the touchline, so animated was he throughout the 90 minutes. Even when his team scored twice in the first half Lennon's reaction was to turn and shout at spectators in the main stand behind him. "Yeah, [I was getting stick from the fans] but that's nothing new, is it?" he said. "It was good timing because a fan shouted I was getting sacked in the morning just as Joe scored."

Lennon and Ledley both made the right noises about going to Turin in midweek for the second leg of their last 16 Champions League tie against Juventus and giving it real go but, with the league all but sewn up, defeat here would have effectively ended Celtic's season.

Instead, the prospect of a domestic double remains very much alive. "There will be pressure on us to win this cup," admitted Ledley. "We haven't done the double yet. Hopefully we can achieve that this season."

Lennon was unsurprisingly unhappy with the goal his side conceded in the first half. There seemed little danger when John McGinn hoisted a ball towards Thompson at the back post but, for whatever reason, Emilio Izaguirre first headed the ball up into the air and then over his goalkeeper's head. It would likely have dropped into the goal, but Goncalves made sure in any case. "The equaliser was a comedy of errors again," sighed Lennon. "We've got to stop doing that."

St Mirren were just as generous, some of their defending bordering on negligence. The two goals they conceded were a case in point. Forrest was at the centre of both, flighting in a cross after just five minutes that found Ledley in splendid isolation to glance a header beyond Craig Samson.

The second came from a well-worked corner that picked apart St Mirren's zonal marking. Forrest worked a one-two with Gary Hooper before crossing to the back post where Stokes, having freed himself from his marker, headed in from a matter of yards.

The game became increasingly scrappy in the second half, although only a fantastic fingertip save from Samson on to the crossbar denied Hooper, Forrest skidding the rebound wide. It mattered little in the end.

"Look, if we'd have lost that could've been the season over competitively," added Lennon. "They've kept it alive. We've got a semi-final to look forward to, a championship to win and a big game on Wednesday. So it's all guns blazing again."