England's hopes of averting a 3-0 whitewash in the West Indies were hit when Ben Stokes emerged as a doubt for the third Test, with Ben Foakes and Chris Woakes also managing injuries.
If the worst happened and all three were ruled out of the game in St Lucia, which begins on Saturday, England would have just 12 fit players to choose from.
Stokes was present at training on Thursday, England's first full session since their three-day defeat in Antigua, but did not take part due to bruising on his right heel.
Foakes, who was hit on the hand by a Shannon Gabriel delivery last week and was unable to keep wicket in the second innings, was involved but has yet to be given the green light by medical staff and Woakes is highly unlikely to make it as he manages a longstanding knee complaint.
England were keen not to make any early assessments, with another full day of preparation work ahead, but Stokes' ability to balance the side as a top-five batsman and reliable seam bowler makes any question mark overs his participation serious.
He would be considered as a specialist batsman even if he was unavailable to fulfil his duties with the ball, but England will give themselves more time to make a judgement.
Restructuring the side, or just the batting order, remain possible but with Adil Rashid having flown home to be with his pregnant wife options are limited.
Of the dozen players who are currently considered 100 per cent fit and available, Keaton Jennings has just been dropped, Jack Leach is a second spinner at a pace-friendly venue and Mark Wood has not played Test cricket since last May.
Wood was likely to make his comeback regardless of fitness issues, his extra speed looking increasingly attractive due to Sam Curran's struggles in the series, but were Stokes' ability to bowl compromised he would become a virtually essential pick.
Speaking ahead of nets, vice-captain Jos Buttler revealed England had been spurred on by wounded pride.
The tourists have seen their techniques and temperaments picked apart since landing in the Caribbean, bowled out for 77, 246, 187 and 132.
Head coach Trevor Bayliss has called them out for lacking "guts and determination" and "will to fight", with Buttler admitting the message had hit home.
"I think as a player when those kind of things are questioned it can hurt your pride, so you want to prove him wrong," he said.
"The guts, courage and determination of the group is very strong. But these are things that certain guys have shown in the past. We have not been good enough to show that at times on this tour and we will be looking to show lots more of that."
Buttler has contributed just 55 runs in four innings thus far, a dramatic drop after averaging 44.70 in the first 10 Tests after his recall.
That sequence included a maiden century against India at Trent Bridge, which remains his only hundred in 52 innings at the top level.
Despite his undoubted talent that is not the return demanded of a top six player, and Buttler is happy to be held to a high standard.
"You expect to be under pressure to score runs. That is your job and that is what you are accountable for," he said.
"That (century) is the best blueprint for me in red-ball cricket, the way I played in that innings. When you experience those feelings and emotions, you're desperate to experience it again.
"It's something I can look back at and draw on as the best template for me to go about it."
