Cusiter's involvement in the RaboDirect PRO12 final in Dublin came to a premature end after 45 minutes, an injury which means he will miss the early stages of Scotland's summer tour, his place being taken by Edinburgh's Grayson Hart. At that stage, Glasgow were just two points behind Leinster, but the 31-year-old admitted that his side were far from their best on a day when their Irish opponents hit top form.
"We didn't play our best game and that is what we needed to do to win the final," said Cusiter. "We made too many mistakes and when we had them under pressure we turned over the ball, knocked on or gave away penalties.
"We never managed to build pressure on them. From that point of view, I am desperately disappointed. All the boys feel the way I think."
On a sultry Dublin evening, Cusiter admitted that conditions had played a part in draining energy from Glasgow, a side for whom fitness is never usually a doubt.
"Both teams were struggling with the heat and the pace of the game and we were clinging on a bit," he said. "We were exhausted. It was a hot, hot day out there. You could feel the fatigue."
After spells at the Border Reivers and Perpignan, Cusiter turned down an offer from Clermont Auvergne to come back to Scotland and sign for Glasgow in 2009. The Warriors had been also-rans in Celtic competitions in previous seasons, but they have reached the PRO12 play-off stages in four of the five seasons since his return.
However, reflecting on his time with the club, Cusiter recalled bleak periods as he struggled with shoulder and knee injuries that kept him out for lengthy spells. "Mostly I have loved it but I wish I had not had the injuries," he said. "They were dark times. There were two seasons when I managed just three games. To be injured for 11 months was not a fun time in my life.
"There were times when I thought I might retire. But this has been my most enjoyable season. I have got a new lease of life and enjoyed rugby.
"So I will leave with lots of fond memories and will be watching the boys when I can. It is a great club."
Cusiter cited the expectation levels of the players and supporters as major factors in Glasgow's rise towards the top of the PRO12 pile. "This season has just gone to another level," he explained. "It's everywhere: that home semi [against Munster two weeks ago] played in front of 10,000 people, the interest around Glasgow, the taxi drivers chatting to you about how well Glasgow are doing, the people in the street. By beating the big teams regularly we have gone to the next level.
"I hope they continue that and I don't see why they won't. Gregor Townsend is a great coach, very astute, and he has recruited well. I am sure he will continue that work next year. If you are competing in finals you are doing something right."
Moray Low, the prop who also played his last game for the Warriors before his summer move to Exeter Chiefs, also predicted a bright future for the players and the club he will now leave behind.
"You look back, five, six or eight years to when Glasgow were a bottom-of-the-league team," he said. "We were written off pretty much every week, but look at where we are now. That culture change has been great. To have been part of that and to be able to leave the club where it is, reaching finals and competing, is great to see.
"The guys will learn from this going into next year and will want to go one further, just as we did last year. Everyone has that desire inside them when they pull that Glasgow jersey on. There is a lot of confidence in this team about next year."
Mark Bennett has been called into the Scotland squad to replace Alex Dunbar, who suffered a hip injury.