Sydney Swans midfielder Mills will be managed through the rest of the season as the gun Sydney onballer continues to deal with an Achilles injury that forced him out of the match against St Kilda just minutes before the opening bounce.

Mills has been managing Achilles tendinitis for much of the season but after missing three matches in recent weeks and with only two rounds remaining until the pre-finals bye, the Swans believe he needs to play regularly to maintain strength and conditioning around the injury.

The 24-year-old has starred in his first season as a full-time midfielder and is averaging 28 disposals with 12 of those contested, five clearances and more than four inside 50s a game.

Mills was also one of the two Swans players who were pulled from their clash with Greater Western Sydney about an hour before the round 18 match, after it was found the players had been exposed to a COVID-19 hotspot and were required to isolate for 14 days.

"If Callum is available to play, we'd prefer him to play because he hasn't played a lot of footy. We need him to play, he needs to play," coach John Longmire said on Tuesday. 

"But if he's not right we won't put him out there, a bit like we made the decision last week. 

"He's been playing with [the injury] for the whole year and with tendinitis you need to keep a certain amount of load going through it. When he was in isolation, he wasn't able to get that training load that he needed.

"Every Achilles tendinitis is a bit different, everyone responds a bit differently. We'll see how he goes on Thursday and make a decision after that from week to week."

James Rowbottom replaced Mills in the 22 that started the match against the Saints and delivered his most influential performance for several weeks with 14 disposals, five clearances and five tackles.

The 20-year-old has been in and out of the team over the past month and Longmire revealed that Rowbottom has instead focused on training and strength work to return to fitness after knee and rib injuries earlier in the year.

"He's had a pretty tough year. No matter whether you're a young player like James or an older player, you need to be able to do that continuous training, work on your craft," Longmire said.

"He was able to get to games but not able to get to training, so we took the decision to make sure that we got the training in as a priority.

"He obviously came in late on the weekend for 'Millsy' and we thought his pressure around the ball was pretty good. His pressure at the contest and his power at the contest was pretty good, so that's a good sign."

The Swans have had a fortunate run with injury for much of the season and currently have luckless ruckman Sam Naismith as their only long-term concern.

Youngsters Braeden Campbell and Chad Warner are ready to push for selection after overcoming injuries that sidelined them through the middle part of the season.

Campbell has now had four outings at the lower level since recovering from shin soreness that disrupted his first season, while Warner has played one and a half scratch matches as he looks to add to his 12 matches for the season before the Swans begin their first finals campaign since 2018.

"Whether they play this week or next week, or what happens from there we're not sure yet, but they're certainly coming back into the frame now," Longmire said.

"They've got some special qualities, both of those boys. They play with speed and power and they're two really unique qualities to have.

"Even though Chad is only in his second year and Braeden is in his first year, a bit like Errol [Gulden], they're players that you know can come into the senior team and contribute and help you be competitive."