And the Highlanders talisman said he is still undecided on what he is going to do next year.
Thomson played his third game for Otago this year and, after being in the All Black camp for the past two months and not getting a lot of game time, he struggled to remember the last time he played a full game.
"It was tiring. It has been a while. I was a bit rusty at the start.
"At this level the defence was a little bit lacking and that loosens it up, and that makes for a lot more running," Thomson said.
"We had to really tighten it up and full credit to them [Tasman]. They took those two intercepts.
"I just said 'we are the ones making the play here. A couple of intercepts - you can wipe those off because we are making the inroads down there. As long as we are patient and hang on to the ball we'll score points' and that is what happened."
Thomson started on the blindside flank and then shifted to the openside in the dying stages of the first half. He made a couple of key turnovers in the second period as Otago started to get on the front foot in the game.
He felt he would be better for next week with Otago in the final, either against Southland or Counties-Manukau.
As for next year, Thomson (30) said he had still made no decision on where he would be playing.
"I'm still working my way through it.
"I would love to come back here. I love Otago and the Highlanders. But I've got a few things to work through first."
He was not setting any deadline on deciding where he would end up and did not commit to saying he would head overseas.
"It is the same old process. You do not want to rush into these things. You want all the options there to make an informed decision and that is what I am doing."