New West Ham signing Lucas Neill will be out of action for up to three weeks with the ankle injury he picked up on his debut against Watford on Saturday.
Neill (l) and Ashton are both suffering from ankle injuries
The Australian defender was forced off on 48 minutes after falling awkwardly and could miss three Premiership games.
And striker Dean Ashton has suffered a fresh setback in his recovery from a broken ankle after five months out.
Ashton needed an injection in his ankle and cannot resume training as planned - with a first-team return some way off.
Neill, 28, has suffered an inversion sprain to his ankle.
He will definitely miss Tuesday's game against Liverpool and the trip to Aston Villa on Saturday but could be back to face Watford on 10 February.
Dean is now to rest for four days before being re-assessed when he hopes he will be given the all-clear to resume his fitness work
West Ham physio Steve Allen
West Ham physio Steve Allen said: "His estimated recovery time is two to three weeks, but we are hopeful that he could be back sooner."
Hammers boss Alan Curbishley has already said he thinks it will take Ashton five weeks to be in contention for the first team when he does progress from basic fitness work.
Ashton, 23, went to see a specialist at a sports rehabilitation clinic for an assessment of the problem.
Allen explained: "He discovered an area of scar tissue that was impinging on the front of Dean's ankle, causing him discomfort when running at a certain pace.
"This has subsequently been injected under an ultra-sound scan and Dean is now to rest for four days before being re-assessed when he hopes he will be given the all-clear to resume his fitness work and push on to full training."
Despite the delay to Ashton's return, Curbishley says he will not be making a bid to sign striker Darren Bent from his old club Charlton.
"We have not made any bid for Darren," Curbishley said. "It was made quite clear to us by Charlton Athletic that the player was not for sale, and so that is the end of the matter."