FORMER Cat Josh Walker says he has the inside knowledge to help the Brisbane Lions spring a surprise victory over Geelong on Sunday.

The Lions recruited Walker this season after five years at Simonds Stadium, and the key forward says he'll pass on everything he knows to coach Justin Leppitsch.

"I think I know pretty well what a lot of their players were working on for five years behind closed doors," Walker said on Tuesday.

"I think there's definitely some tips I could give boys who maybe have an individual match-up.

"I think there's definitely some things I can help the team with.

"They'll know my game but I'll know theirs as well, and I'll be able to give the coach a few insights on the rest of the team. Hopefully it's advantage us."

The Lions will start huge underdogs and will need any inside knowledge Walker can provide after losing their first two matches against West Coast and North Melbourne.

While the Lions have competed strongly, but inconsistently, over the first fortnight, Geelong has beaten premier Hawthorn before coming back to earth with a loss to Greater Western Sydney.

Walker says he expects that defeat to hurt his former teammates and spur them to a big home opener.

"They will be on the rebound and pretty fired up to play their first game at home," he said.

"Hopefully we can catch them while they're down if anything, and continue to play some promising footy.

"We've shown it in glimpses for part of our season so far and hopefully we can put it together for four quarters."

Walker played 33 games with Geelong, including 16 last season, and said he would be nervous playing his former teammates, but comfortable in the knowledge he knew both the opposition and the ground well.

"I've been trying to not think about it too much," he said.

"(I'm) a little bit nervous in that it'll be something a bit different, but at the end of the day it's just a game of footy."