Opener Marcus Trescothick and all-rounder Andrew Flintoff are injury doubts for England's first triangular series match against New Zealand at Old Trafford on Thursday.
Trescothick twisted his left ankle during fielding drills in training and will have an x-ray later on Monday. Flintoff is battling to overcome a foot injury.
"Tresco is meant to have done this before and said he thought it would be all right — but you never really know what's exactly happened until 24 hours later," England coach Duncan Fletcher told the ECB website.
"I like to look on the positive about these things because it could give another guy an opportunity, but it is a big blow for us because they are two major players for us.
"Freddie (Flintoff) is especially a key player, but Tresco has also been outstanding for us.
"You never know what is going to happen at this stage and Tresco might play, but Freddie is looking no more than 50-50 at the moment."
West Indies, who play New Zealand at Edgbaston on Saturday, complete the series line-up. The final is at Lord's on July 10.