Essendon could welcome back forward Will Snelling and midfielder Nik Cox against Adelaide at Marvel Stadium on Sunday, with the pair facing fitness tests.

Snelling is yet to feature this season, having reported calf tightness ahead of round one, while Cox hasn't played since injuring his ankle Brisbane in round two.

Their returns would bolster the Bombers, who reported a clean bill of health from last week's loss to Melbourne.

"'Snells' is back into full training this week, so he’ll need to get through main training later in the week to be available to play," head of high performance Sean Murphy told the Liberty Performance Update.

"He’s had a really good rehab process and that calf hasn’t had an issue, it’s been a seamless recovery. It’ll be good to get him out there and playing some games.

"Cox is a test for this week. He needs to get through main skills later in the week. He’s still working through that ankle but he’s certainly improved and will hopefully be available this week."

While unavailable this week, exciting young forward Harrison Jones is also nearing a return from an ankle injury.

The 20-year-old broke through for his AFL debut last season, playing 16 games and booting 20 goals.

"'Jonesy' is starting to get a good bank of work in now. He’ll integrate back into main training this week and then the plan will be to build him up, so hopefully we’ll see him in the next couple of weeks," Murphy said.

Midfielders Zach Merrett and Kyle Langford have undergone surgery for their syndesmosis and hamstring injuries respectively, with the pair still facing lengthy stints on the sidelines.

"Merrett had surgery for the tightrope (surgery technique) for that syndesmosis injury. He’s now in a boot and walking around," Murphy said.

"The first two weeks (post-surgery) are the most important part, so we’re respecting the healing process there. Once that two weeks is up, we’ll get him going from a rehab point of view. Hopefully we’ll see him sooner rather than later.

"Langford had surgery last week and all went really well. Now it’s just about recovery over the next couple of weeks, and then we’ll get him going from a rehab process."

Promising young defender Zach Reid made his long-awaited return from a foot injury via the VFL on Saturday in limited game-time.

Murphy said the No.10 draft pick had responded well and would ramp up his game loads.

"It was great to see Zach Reid out there playing footy. He played just a bit over 60 minutes, so the plan will be to step that up this week, and then he’ll be playing normal game time," he said.

"He felt really comfortable. He’s done a bank of work over the last couple of months, and his work-rate in the game was really good."

From a performance perspective, Murphy touched on big numbers highlighting the work-rates of Matt Guelfi and Peter Wright. Watch the round four Liberty Performance Update below.

INJURY LIST - RD 4