W hat do they say about one door closing?

Whatever version of that platitude you come up with, Calum Forrester was in no mood to believe it a year ago when he was taken aside and told that his six-season career at Glasgow Warriors was about to come to an end. As far as he was concerned, his life in sport had just hit the rocks.

Yet 12 months on, a rejuvenated Forrester is preparing to lead his Ayr team-mates into the final of the RBS Cup at Murrayfield next weekend against Melrose. The occasion has become something of a fixture in the diaries of the men from Millbrae, but their fourth consecutive final appearance brings the added incentive of a notable league and cup double for a group of players who tied up the RBS Premiership title a couple of months ago.

Good for them, but better still for Forrester, who missed a large chunk of his final season at Glasgow with a serious knee injury, but still felt he had what it took to make his living in the professional ranks. As, indeed, did the Murrayfield authorities who offered him a Scotland sevens contract by way of compensation, but the powerful loose forward had already decided it was time to move on.

"Last season was very stressful," the 25-year-old said. "I was injured for about nine months in total and that's a lot of time to have doubts about your future preying on your mind. I had had a few knee injuries in the past, but that was definitely the toughest to come back from.

"The funny thing is that I had managed to get myself really fit while I was out, so when I did get back out there I thought I was playing some of the best rugby of my career. I was thinking I could really make a go of it. It was a pretty positive time, but then it was made clear to me that I wasn't being kept on, which was pretty hard to swallow.

"I talked things over with my agent. The things we were discussing involved maybe playing in the Championship in England, lower division stuff. But that's not always a great option because some of the sides are full-time and some part-time, and I started wondering if I would only be going in the hope of being picked up by another club. In the end, I just decided that I had had a few good years with Glasgow and it was time to get on with real life."

Fortunately, Forrester had already laid some foundations in that area, completing two years of a sports science and physiology degree at Glasgow University before becoming a full-time player. "Any chance I can come back?" he asked the university authorities. "Happy to have you," they replied, and his mind was set.

And he is in it for the long haul. As a schoolboy, Forrester's ambition had been to become a doctor, but he switched to sports science as it seemed to be a better fit with his rugby interests and commitments at the time. But the lure of the stethoscope is still there. The plan now is to finish his current degree, then switch to medicine in the autumn of 2014.

"If I had carried on as a pro player then this wouldn't have been possible," he said. "If I had stayed fit and injury free and played till I was 31 or 32 it would have been a different story for me. But the way things worked out, I decided this was the path I wanted to follow."

What do they say about another door opening? But while Forrester has regained his taste for the Groves of Academe, he has also learned to love rugby again, rekindling his affection for the simple pleasure of playing for enjoyment rather than a weekly pay cheque. It helps that he was connected to Ayr in the past via the professional draft system, but the rules forbade any involvement in the RBS Cup so next week's match at Murrayfield will be a whole new experience for him.

And his enthusiasm is enough to dynamite any suspicions that he feel he is slumming it in the club game after all those seasons in the elite ranks.

"This is a very ambitious club," Forrester said. "Kenny Murray is a really knowledgeable and experienced coach, the training sessions are great and the support is really good too. For an amateur club, it's a very professional set-up and that has made the transition a lot easier."

It was not so easy at the start. Glasgow warmed up for their new season with a training match against Ayr, and Forrester subsequently went along to Scotstoun to watch his old team-mates in their first match of the season.

Forrester said: "They invited me and my dad along, which was nice, but after a while I was thinking, 'I really don't want to be here right now, this is really strange'. I didn't like being there and not being part of it. I think it's the same for a lot of professional sportsmen; it's tough going back into that environment.

"I was watching them recently, too. It's still hard as there is still a wee bit of me that thinks I could still do it, but at the same time I still have a lot of good friends there and it is good to see them doing well."

Although Ayr went down 24-10 to Gala in last year's RBS Cup showpiece at Murrayfield, they had beaten Melrose in the two previous finals, an achievement that might bestow a certain psychological advantage as a number of the players involved in those games are still stalwarts of the side. As Melrose struggled for a time in this season's league campaign, there might be yet more cause for confidence in the Ayr ranks, but Forrester sounded a cautionary note.

"They have a very good pack and a good set piece," he said. "We struggled against them at times this season. I think they had a lot of players missing earlier in the season, but they seem to have them back now and they've been very strong over the past few weeks.

"They can go wide as well so they will be coming at us from all angles. But that's something we can do, too, so it should be a very good game."