SYDNEY Swans ruckman Shane Mumford feels he's still a few weeks away from his best, but is ready to lift for the challenge of Geelong and show the reigning premiers what they let go.

Mumford spent six weeks on the sidelines due a back infection earlier this season but was able to play two matches before the mid-season bye and will line up in Friday night's SCG clash with the Cats.

"My body's pretty much right now - but the match fitness is something you can't emulate in training," Mumford said on Tuesday at the launch of the club's new environment program for schools.

"Hopefully, I'll be back to my best in the next few weeks .. it usually takes five or six games under your belt."

Mumford has been pinch-hitting up forward more than he's accustomed to, as coach John Longmire attempts to ease the 105kg weapon back into the rigours of AFL.

But the Cats won't need any reminders of what he's capable of in the ruck.

Now in his third season with the Swans, Mumford launched his career with Geelong before seeking greater opportunities in the Harbour City - where he transformed into one of theLleague's best ruckmen.

Meanwhile, with Nathan Vardy injured and Brad Ottens retired, the Cats needed to draft 29-year-old Orren Stephenson last year to boost their ruck depth.

Some might think there's room for regret with that picture, but Mumford noted he may not have been picked for last year's Grand Final, or even improved in Geelong.

"I'm not [regretting it] at all. I'm really happy up here and I probably wouldn't have developed the way I have if I hadn't got the opportunity that Sydney gave me," he said.

"Sydney gave me that opportunity and confidence to play good footy."

The 25-year-old said there was little drama concerning a clash with his former teammates, but admitted to a stern desire to "show them what they're missing out on".

"You always want to play well against the old team.

"Obviously, you want to play your best every week, but the old side gives you that little bit of extra motivation.

"... Last year's premiers - what better challenge going into the second half of the year to really help us secure that top four spot?"