A TRAINING mishap has ended Essendon defender Patrick Ambrose's hopes of returning to the senior side this week against Port Adelaide.

Ambrose, 25, was on the cusp of selection after missing the past six weeks with a quad problem, but tweaked the injury in the Dons' final main training session for the Power clash.

"We were in our last training session before he was due to return to play," high performance manager Justin Crow said.

"He was punching a ball and felt his quad again.

"There is really no option now but to take our medicine and take another six weeks to get that right.

"It's disappointing news for Paddy – there is a bit of a fresh bleed in the quad, so we’ll reload him and build him back up from here."

Ambrose has become a key part of Essendon's defence in the past two seasons.

Midfielder Darcy Parish will also miss Saturday night's match with the Power, but is expected to be fit to play against Sydney after Essendon's bye next week.

Parish suffered a calf injury in the lead up to round 11 and missed the meeting with Greater Western Sydney.

In better news for the Bombers, veteran half-back James Kelly is expected to return for the Port Adelaide match.

"He had some low level groin issues. He'd had a history of that in the earlier part of his career," Crow said.

"He's much better for having the week off and he'll do all of the training, and we'll expect him to play."