But skipper Tom Harley is a strong chance to play his first game since being knocked out in the 2008 grand final.
Ablett sat out most of the final term while he received treatment to his hip/groin region but Thompson said the injury wasn't a major concern.
"He's a little bit tight in his groins. Gary has a history of doing that and it's just total management," Thompson said.
"He's a little bit sorer than normal and with a six-day recovery we'll really have to see how he pulls up, but we won't be taking any risks with Gary. If he's not right, he won't play.
"[But] we're not overly concerned at all. He does get tight groins periodically and some weeks pull up tighter than others. He may miss a week but it wouldn't be any more, I wouldn't think. We're certainly not going to play him to make him sore."
Geelong plays Sydney Swans on Saturday but will need to improve on Sunday's performance against Melbourne.
The Cats broke the record for most possessions in a game with 498, but Thompson was frank in his reply when asked if he had seen anything to smile about in the performance.
"Not really, not too much," he said.
"We're rapt we won. I was pleased we were able to come back and change the way we were playing - we used the corridor more and had a lot of shots at goal [but] no.
"Not that much pleased me really.
"[But] it wasn't a bad day at the office. To win by 43 points against any team is a reasonable day's work. I was never thinking about losing at any stage, we had it pretty much under control.
"We can't always play our most exciting, ruthless, pressurised football. It's just impossible to do it every week."
The Cats looked out of sorts during a first term in which the Dees led nearing quarter-time, and never quite hit top gear.
"I think we scored easy goals in the first half and didn't play great footy and I thought we played better football in the second half but never got a score," Thompson said.
"Obviously we missed a lot of opportunities - our forwards kicked 14 behinds between them and it's not good enough.
"It's hard because I promised myself I wouldn't get angry today. That we'd just try to look at things rationally, if things needed fixing up then we'd fix them up - and we did up to a point.
"There were four or five things we asked of them at quarter-time and by the end of the game they were fixed up and that's a real positive."
The Cats inaccuracy at the MCG continued on Sunday with a return of 15.21.
That followed their shocking 11.23 in the 2008 grand final, 15.21 again in their round one win over Hawthorn, and a better return of 18.14 against Collingwood in round three.
That represents a wasteful four-game total of 59.79.
