Scarlett was initially expected to miss just one week after he strained his back in the bruising second-round clash against Hawthorn, but Sunday's game against Richmond will mark a month on the sidelines.
"He's got a pretty tight back naturally and he just hasn't been able to do a lot of running," Thompson explained from Skilled Stadium on Thursday.
"The last three or four days he's been able to run a little bit more, but now we just don't want to put him in until he's 100 per cent right.
"We're pretty certain he'll be right for next week."
Joel Corey was a late withdrawal from the side that suffered a disappointing loss to Carlton on Monday and his knee hasn't come up despite the break.
Thompson reported that just three days on from that clash, several players would still be undergoing scans on Thursday night, making the named squad subject to change.
"We don't know who we're going to play and we'd probably like to name 33 in the squad tonight to make sure we've got things covered," he said.
"You might see the squad and you might see some changes. We can't do much about that and we don't want to scare people, it's just the fact that we played three days ago and it's very hard to put a squad together."
The coach's indifference toward the 33-possession effort of star onballer Gary Ablett immediately following that game brought some criticism his way, but he stood by his appraisal having reviewed film of the match.
"People watch a game differently to what coaches do," he said. "Gary, even though he won his own ball and he's terrific at that, played in a midfield that was really easy to play against.
"He's not happy with that part of his game, but we're not just blaming him for that, we're blaming the whole group. The whole team was too easy to play against and we've got to accept that. You can't hide from it.
"We're not here to entertain. We'd love to see Gary kick unbelievable goals, take marks, have five bounces and all that stuff that looks great, but in the end that doesn't win you games.
"What wins you games is stopping the opposition from scoring as much as you do."
While the whole team attracted the wrath of Thompson, he defended the performance of key forward Tom Hawkins who failed to register a kick against the Blues.
Thomspon said Hawkins played his role and will definitely be in the side for this weekend.
"He didn't play as bad when we watched the film as what we thought at the time," he said.
"He wasn't the only one to play poorly; I thought we all played below the level of what we expect. Tommy is no different to anyone else.
"We don't judge from week to week - we go with a long-term view and we are going to play Tommy. We still think he's going to be a terrific player - we have no doubts about that at all."
Thompson said he had warned his players not to expect to just turn up and go through the motions against the winless Tigers who he believed would have been a chance to beat his side last week.
Mathew Stokes is still two weeks from resuming as he serves the rest of his club-imposed suspension, but Thompson was relieved at the resolution of his drugs case on Tuesday.
"The whole incident has been hard for us and has been embarrassing for the club and Mathew," he said.
