A MUCH-CHANGED St Mirren side staged a second-half fightback to stave off the spectre of a Petrofac Training Cup upset.

Despite his side losing their opening two Ladbrokes Championship games, Ian Murray, the St Mirren manager, used last night's third-round tie to field some of his fringe men – making seven alterations to the side that lost to Dumbarton on Saturday.

The move looked in danger of backfiring when Ladbrokes League 2 side Annan went ahead within a minute. However, goals after the break from Jordan Stewart and Alan Gow ensured St Mirren made it to the last eight and gained a much-needed morale boost ahead of Friday's Renfrewshire derby at Morton.

"The changes weren't in any way meant to disrespect the game or anything – it was still a competitive team we put out," said Murray. "We got there in the end, but it was a tough night. I thought Annan did exceptionally well and gave us a real wake-up call. We're not up to pace with where we want to be, so to get through the tie with a win was the most important thing."

Goalkeeper Jamie Langfield, who joined from Aberdeen last week, came in to make his debut and, remarkably, the veteran's first task was to pick the ball out of the net after Annan raced into a shock lead.

With just 16 seconds on the clock, Jim Goodwin was judged to have fouled Josh Todd in the box and a penalty was awarded. Former Morton striker Peter Weatherson made no mistake in firing the underdogs ahead from the spot.

St Mirren threatened an equaliser three minutes later but Calum Gallagher's header from a Stevie Mallan free-kick was deflected inches past. Cameron Howieson had a magnificent chance to level for the visitors when he burst through the middle in the eighth minute but his tame shot from inside the box was easily saved by Jordan Hart.

At the other end, Weatherson tried his luck from 20 yards but was denied by Langfield. Annan had an even better chance in the 15th minute when Stuart McColm latched on to a long ball over the top but, with just Langfield to beat, he blazed his shot high over. The League 2 side were more than holding their own against their full-time opponents although defender Steven Swinglehurst had to make a vital block to stop Alan Gow's goalbound effort finding the net.

Annan almost doubled their lead in the 28th minute when Todd pinged a 25-yard shot towards the top corner but Langfield did superbly to claw it away for a corner.

The Paisley side threatened in the 39th minute but Gow's strike from just outside the box was palmed away by Jordan Hart and a minute later the goalkeeper had to tip over a Gallagher header. Lewis McLear then volleyed inches wide from the edge of the box as the Championship outfit.

Annan started the second half on the front foot, with Todd seeing a shot from 18 yards out clawed over by Langfield. However, St Mirren drew level in the 51st minute when left-back Jordan Stewart arrived to rifle in a superb low shot after Barry Cuddihy's cross from the right was headed out to him on the edge of the box.

Langfield then had to make a vital save to stop Weatherson bundling in a Martin McNiff cross from close range in the 59th minute. It was to prove a pivotal moment as St Mirren edged ahead seven minutes later when Gallagher burst down the right and into the box before cutting the ball back for Gow to fire a low angled shot beyond Hart from eight yards out.

Substitute Paul McMullan almost extended the visitors' advantage when he smacked a shot against the post.

St Mirren could have done with the extra goal as they were made to withstand a late onslaught from a home side who refused to accept defeat. "I'm gutted for my players because they went toe-to-toe with St Mirren," said Jim Chapman, the Annan manager. "Their goalie had more saves to make than ours, which shows how much we were in the game. If I've got any complaints, it's the naivety and stupidity that creeps into our play so often at crucial times."