Easter sat out the 41-10 win over Georgia last week but team manager Martin Johnson is hopeful he will be available for selection for the crucial clash with Scotland on October 1.
But, with time running out before that game and with Easter ruled out of Saturday's game against Romania, the England coaching staff have set a deadline of this Sunday to confirm whether or not the 33-year-old will play any further part in the competition.
"Nick's progressing. We'll see where we are after Saturday," said Johnson, whose men will be looking for a third pool win against a Romanian side who have lost both their opening Pool B fixtures.
"Nick's not had this injury before, it's just one of those where we're hoping he's going to be good to go next week.
"All the signs are he will be. It looks good but these things are day to day. We've got to (make a decision) after the game.
"I think Nick will be okay. He's desperate to get back and play but we'll see how it progresses over the next 48 hours."
Johnson has already called up New Zealand-born and bred Thomas Waldrom as temporary cover for Easter, while James Haskell impressed at the back of the scrum against the Georgians.
The former Wasps and Stade Francais star will start there against Romania, with Johnson happy enough with his options if Easter is forced home.
"Nick'd be a loss. That's why we had guys in through the camp. Thomas was in learning what we do, so if the situation arises he can put himself in contention pretty quickly," added Johnson.
"Haskell came in last week for us at short notice and he's done very well. He's keen to improve and when he's been in the team, he's often covering multiple positions depending on who we have on the bench.
"At times he's covered all three, so he has to know all those roles and he's done a good job of it - he's playing well and he's a useful player to have with his utility."
England are still to replace injured Lions prop Andrew Sheridan in their 30-man squad, with that decision also expected to arrive shortly after this weekend's match.