GEELONG'S defence will be undermanned for the NAB Cup competition, with All-Australian duo Matthew Egan and Matthew Scarlett to miss the Cats' opening match against Melbourne.

Egan has hit another hurdle in his bid to recover from a broken foot, while Scarlett underwent an arthroscopy on his left knee on Thursday to remove what the club called, 'loose bodies'.

Egan is to have surgery next week to remove one of three screws that were placed in the fractured bone last year. The screw that was situated on the outside of his foot was causing irritation, and was expected to cause larger complications had it been left untouched.

Geelong general manager of football operations Neil Balme said the problem wasn't classified as a "setback", but admitted it will put Egan's rehabilitation slightly behind schedule.

"It's not ideal, but it's been recognised as necessary," Balme told afl.com.au.

"With the feet, they're always a bit problematic, so we're pleased that they've recognised it and they've taken a positive step to try and fix it.

"It'll put him back a little bit, but not too much, we don't think."

Balme also said Egan's return to training after the operation will depend on how the foot settles without the third screw, and that the All-Australian was looking strong before the injury flared again.

"He was doing a reasonable amount of running before this, he wasn't fully involved but he was doing quite a bit of running, and with those feet, you do a bit of work, you push it to a certain limit and sometimes it gets a bit sore so you pull back," he said.

"He's been up and back a little bit from that point of view, so we were reasonably pleased with what he was doing.

"He was getting a bit of constant soreness in one area and they did a scan and realised there might be something indicated by that screw, so they decided to fix it."

There is no set time frame for Egan to return to the game, but the defender was already expected to miss the NAB Cup before the latest problem was discovered.

The 24-year-old initially broke his navicular bone in the Cats' final home-and-away match of 2007 against the Brisbane Lions at the Gabba. He then embarked on a race against time to be fit for the club's historic assault on the Grand Final, but missed the entire finals series and watched the premiership win from the sidelines.

He then reportedly suffered complications with the healing of the bone, which has proved to be a tricky injury for AFL footballers to overcome in the past.

Balme also said Egan is remaining a "pretty resilient guy" despite the frustrating nature of his injury, and is in good spirits despite not knowing when he'll be right to play again.

Scarlett, who played every game bar one in 2007, has been ruled out of appearing in the club's first competitive hit-out at Skilled Stadium following his minor operation.

"He's fine, he's been done. It was really just a 'clean out'," Balme said.

"He was a little bit sore, he had a bit of floating debris, which they fixed. He's never had problems with his knees before, so he'll recover 100 per cent from that reasonably quickly.

"It will probably just be a couple of weeks for that."

Meanwhile, Travis Varcoe will also miss the encounter with the Demons after having his tonsils removed on Wednesday.

"I think [the tonsillitis] has been around for a while, and they're reluctant to operate but it's been giving him trouble over the last 18 months, so they've finally decided to do something about it," Balme said.

"That'll just slow him up for a couple of weeks, and then he'll be fine."