Tonight he puts all that behind him when he not only makes his first start of the season for Glasgow, but also runs out as captain.
True, he has had a couple of runs from the bench but that is not the same challenge as managing a game from the start, and one man who is clearly delighted to see him back in action is Gregor Townsend, his former half-back partner at the Borders, now head coach at Glasgow.
Townsend admitted that with Henry Pyrgos having emerged as an international scrum-half during Cusiter's absence and Niko Matawalu, the livewire Fijian, due to return to action within the next fortnight after breaking a bone in a foot, selection is about to become a major headache. It is, however, a part of the job he enjoys, the coach claimed, though breaking news of his decisions to the players can be less amusing.
This week, however, it was easy. Matawalu is still recovering, Pyrgos has started every game including the pre-season warm-ups and needs a rest, while Cusiter has been flying in training, has made a significant impact in a couple of runs off the bench and is raring to go.
"As a squad we will always have players who are out long term," Townsend said. "We did miss him but the guys who came in played really well so there is plenty of competition now with three very good scrum- halves competing for that jersey
"He has trained very well, his handling in the wet was excellent. He is an international captain. He was out for 11 months so it is great to have him in the team. He is loving his rugby again, it is a great boost for him.
"He is very competitive, he has said to me how much he has enjoyed getting back and stuck into people around rucks — that is what he missed the most though he did not realise it until he got back out there. He will run and tackle hard; he has excellent basic skills as you would expect of any international scrum- half, and he has the experience.
"He has played against Leinster a few times and is enjoying just playing again. He has a real knowledge of the game, quietly spoken but makes really important points. He thinks long and hard about what our aims are this week, and has a lot of respect from the team, from the way he trains, what he has achieved in rugby and his personality."
Cusiter aside, the only change in the back division from the side that started in the dramatic late victory in Belfast last week is that Alex Dunbar returns at centre with Sean Lamont shifting back to the wing and Tommy Seymour, another who has played every game, making way.
The significant changes are in the pack where Jon Welsh gets his first start in his new role at tighthead prop hoping for an extended run after Mike Cusack gave up hoping his shoulder would get better with rest and had surgery to repair it earlier this week, nine months after he originally damaged it.
Back-row rotation means Chris Fusaro and Richie Vernon are back in the starting XV as Townsend seeks to go for pace rather than power to try to get the better of a side that have become something of a nemesis for his club in recent seasons, winning six of the last seven games with a draw in the remaining fixture. Glasgow have not beaten them since 2010.
"Beating them would be a massive achievement, they have been the best team in Europe the last three or four years. I found out a couple of days ago they have only lost once in their last 20 games. We played them three times in that period and though they were really close games, they won all three," Townsend said.
"We are up against a team and a squad that have been very consistent and play a very successful brand of rugby."
Not that it is the most formidable team that Leinster have available. They are still easing their Lions back into action, with Brian O'Driscoll, Sean O'Brien and Jamie Heaslip still waiting for their first action while Cian Healy and Rob Kearney are both being eased back via the bench.
They were held at home to a draw by the Ospreys last week, so they are not looking as invulnerable as Townsend was suggesting, and with a sell-out crowd expected at Scotstoun tonight, there is no reason why Glasgow should feel in any way inferior.
After all, they broke a four-year duck in winning in Belfast last week, so this is the perfect time for them to break a three-year run against Leinster and give themselves their best start to the season for more than a decade. The last time they managed to open with three wins was in 2002-03, when, coincidentally Leinster were one of their victims back in the days when the Celtic competition was played in two groups.
They are going to have to play better than they did in Ulster, where they seemed to fall asleep for about half an hour and were lucky the home side dropped two scoring passes, but Townsend believes Cusiter can be the talisman that produces the performance he is gunning for.