Essendon defender Aaron Francis has suffered another setback in his bid for a senior debut.

Francis hurt his quad in the first 15 minutes of the Bombers' 28-point VFL loss to Sandringham.

Francis, 18, tested his leg in an attempt to return but with the club unsure if he had suffered a strain or a corkie, they took a conservative approach and sat Francis out for the rest of the match.

The Bombers will know more after it settles down, with Francis likely to have his quad scanned.

It has been an unlucky beginning to his career after being taken at No. 6 in last year's NAB AFL Draft, with a calf tear earlier in the season restricting him to just three VFL games.

After showing impressive signs, Francis was being touted for a senior debut, although coach John Worsfold last week cautioned against too many expectations.

"[He's] not ready for AFL yet. I think that would be the wrong thing for him and not the best thing for the team at the moment," Worsfold said.

"We'll measure him week on week and see how he's tracking and how he pulls up.

"It still does depend on his form and he's going to have to work and play really good footy to get his spot in the team.

"Right at this stage I'd say he needs to play a couple of really good games, so plug that into where he's at at the moment, [a debut] is at least three weeks away I would guess."

Essendon lost by 108 points to Hawthorn last Friday night and faces another tough task against Greater Western Sydney at Etihad Stadium on Sunday afternoon.

Key defenders Michael Hartley (hamstring) and Nathan Grima (hip) are likely to be unavailable.