CAPTAIN Adam Simpson says the Kangaroos' backline faces itsbiggest challenge yet against St Kilda on Sunday.

While Simpson thought defenders Michael Firrito, JoshGibson, Daniel Pratt and Drew Petrie have been "really holding theirown" this year, often against taller opponents, the Saints' trio ofpowerful forwards looms as a huge assignment.

"I think our back six has been a real starting pointfor our team, they are very reliable one-on-one," Simpson said.

"We don't have to necessarily drop players back to helpthem out. We can back them in to win their own contest.

"If they can do that, then the team sort of flows onfrom there."

Key defender Shannon Watt has been sidelined for the pasttwo matches with hamstring tightness but is a strong chance to return.

Simpson said Watt only just missed selection last week.

"If he's right, I'm sure he'll play," Simpsonsaid.

Whether they can stop full-forward Fraser Gehrig, co-captainNick Riewoldt and Justin Koschitzke will also depend on how the football isdelivered into the forward line.

That task will fall to the Kangaroos' midfield, whichSimpson said was determined to bounce back after being soundly beaten in lastweek's loss to West Coast.

"They've got some talent up there and if it comes in aseasily as it did last week, we'll be in trouble," Simpson said.

"It's our responsibility as well to stem the flow.

"That's why this week is so important, to make sure [lastweek] was just [an aberration]."

The Kangaroos' six-match winning run ended at the hands ofdefending premier West Coast, dropping the team to a 6-4 win-loss record.

St Kilda has lost its past three matches to sit outside theeight at 4-6.

Simpson said the next two weeks before the mid-season breakwere important for both teams.

"We've got the Saints then Adelaide, you drop those two and you'reoutside the eight," Simpson said.

"They are in the same boat so it's going to be prettyred hot. They are just as keen as us to bounce back.

"Your season is really set up this time of year. If yougo into the break behind the ledger you're in trouble."

Meanwhile Daniel Wells, who is out with a knee injury, hasresumed running.

Simpson said Wells was an outside chance to play against Adelaide, although theexciting midfielder was more likely to return after the break.