England are likely to be without Dan Cole and Mako Vunipola during the November Tests, with the duo still recovering from respective injuries.
The news was revealed at Wednesday's Aviva Premiership launch in London, where Leicester and Saracens' bosses offered injury updates.
Stuart Lancaster's outfit are set to take on New Zealand, South Africa, Samoa and Australia in the fixtures ahead of the World Cup and will want their top players peaking at just the right time in 2015.
"Coley has had the all-clear from the surgeon to ramp up his training and that was a week ago. He should be fit about 12 weeks from that date, so we're hoping Dan will be playing again in 10 or 11 weeks, but we will see. We will give him as much time as he needs. The disc that has been replaced will be stronger than the one he had in there in the first place," explained Leicester Tigers director of rugby Richard Cockerill at the launch.
"We will listen to the specialists to make sure that when he comes back, he is good to go. It would be nice to have him back within the 12-week timescale but if it's a month later, two months or he doesn't play until April, it is what it is.
"It's far more important that he gets his neck absolutely right rather than come back a bit early and have issues with it. Stuart Lancaster is very sensible about it. Coley will be ready to play when the specialist deems he is ready and not before.
"The disc has been replaced. It is a metal disc - there's a plate and a ball-and-socket joint inside. He has been letting the bone heal and has done nothing at all for a few months, but now he can start doing some cycling, some running, some light weights and gradually build himself back up."
Meanwhile, Vunipola's recovery from a knee injury is progressing but director of rugby Mark McCall said the prop is unlikely to return to club action with Saracens before November.
"Mako has an injury from the European final. He;ll be out for a while - until November possibly. But he has no chance for the autumn internationals," he confirmed.