ESSENDON coach John Worsfold doesn't know why Conor McKenna bit Western Bulldog Tory Dickson, but he's put the incident down to a "brain fade" by the defender.

McKenna was suspended for three weeks by the AFL Tribunal for the indiscretion in last week's lost to the Bulldogs.

Dickson chased down the Northern Irishman as he was dashing from defence, and the bite took place as the pair wrestled on the ground.

Asked by reporters on Thursday why the 22-year-old reacted like he did, Worsfold said he hadn't asked McKenna the reason for the bite. 

"I don't really want to know why," Worsfold said. 

"In the heat of the moment and in the fraction of a second after he (McKenna) has just sprinted for 100 metres, got run down and was disappointed (he got) tackled. 

"A bloke is pulling him down and he's trying to get off and something happens in a fraction of second, do you think he thought through it? 

"Why (has biting) happened in previous times, why have players been reported for hitting guys off the ball? 

"It's a fraction of second brain fade, a lack of concentration, fatigue, stress, there are a lot of factors that go into it, (so) I can't answer.

I've said (to Conor) things happen in footy, we make wrong decisions at times and we deal with the consequences, we don't dwell on it and we focus on being better." 

Worsfold floated several players as replacements for McKenna, with first-year midfielder Matt Guelfi a chance to debut against Port Adelaide on Sunday after the West Australian received a massive cheer from the playing group before training.

Patrick Ambrose (wrist) and Ben McNeice (hamstring) have both recovered from injuries, while Michael Hartley could be recalled after being dropped for clash with the Bulldogs.

"Ambrose has been passed fit, providing he gets through (training), Hartley is available, Ben McNeice is now available as well, so they're names we'll certainly look at," Worsfold said.

"Mason Redman did really well on the weekend (in the VFL), Jordan Ridley is getting back to full match fitness and is an exciting young player as well." 

Utility Aaron Francis won't play in the VFL as he resumes from off-field issues, but Worsfold said the 20-year-old was "tracking really well" and would be ready to play sooner than later.