Saracen Daly's knee problem could keep him out of England's opening World Cup clash against the Pumas in Marseille on September 9.
If the 30-year-old fails to make the Pool D opener, England could be missing more than a third of their preferred starting XV.
Anthony Watson was ruled out of the entire tournament yesterday with a calf injury, with the luckless wing likely to be replaced by Jonny May in England's 33-man squad.
Head coach Steve Borthwick has held off confirming the revision to his 33 for France until after tomorrow's final warm-up, against Fiji at Twickenham — and with good reason, given the steady stream of bad news.
England are confident Daly will be fit to start the World Cup, but fears have grown about his chances of contesting selection for that crucial opening clash.
Tom Curry has not featured across the entire warm-up schedule with an ankle problem and remains another doubt to start the World Cup. Captain Owen Farrell and No8 Billy Vunipola will sit out the opener in France due to suspension, leaving England potentially without five of their first-choice XV.
Throw in the previous injury-enforced withdrawal of Jack Van Poortvliet at scrum-half, and England's outlook appears increasingly clouded. Lock George Martin has a knee injury and wing Henry Arundell a back spasm, though their issues are considered minor.
"Part of announcing our World Cup squad when we did was about ensuring that our planning process was clearly in place, understanding where we were and what the contingencies were," said Borthwick. "Did I anticipate this situation? No, but I think the team has adapted really well. We always knew there would be situations we'd have to work around, setbacks to adapt to, and it has brought the team even closer."
Farrell will miss the first two World Cup matches, after his disciplinary saga for a high tackle on Wales's Taine Basham ended in a four-week suspension.
Vunipola will miss two matches for his high shot on Ireland's Andrew Porter, provided he completes World Rugby's tackle school coaching initiative.
England are in desperate need of a morale-boosting win tomorrow, before heading out to France on Thursday.
Jack Willis will start in England's back row, with Saracens' loose forward Ben Earl slotting in for Vunipola at No8.
Willis made a mid-season switch to Toulouse after Wasps fell into administration. He currently has special dispensation to play at the World Cup, as England only select overseas-based players in exceptional circumstances. The 26-year-old could see his England career halted after the World Cup and he admitted his long-term Test future is out of his hands.
"I'm very passionate about playing for England, but it's not a decision for me to make," said Willis. "I had to do what was best for me and my family, and what will be will be. I really want to play for England, but it's not for me to make those decisions."