England centre-backs Steph Houghton and Millie Bright are doubts for their Women's World Cup quarter-final against Norway, says boss Phil Neville.
Houghton, 31, injured her ankle in the Lionesses' last-16 win over Cameroon but took part in training on Wednesday.
Bright, 25, has a sickness bug which Neville said was "going through the camp a little bit".
"Steph is because of the tackle and Millie has a virus, so she is more of a doubt." Neville said.
"We will give them right until the last minute to be fit."
England face Norway in Le Havre on Thursday (20:00 BST kick-off) in a repeat of their last-16 tie at the 2015 World Cup, which they won 2-1.
Houghton is one of three players, along with Lucy Bronze and Jill Scott, to start every game of the tournament so far.
The Manchester City defender has partnered Chelsea player Bright in central defence in three of England's four games.
But Neville said he was "relaxed" about the defenders' potential replacements, Leah Williamson and Abbie McManus, who have both played in the World Cup and have featured several times in Neville's team, including at the SheBelieves Cup.
"You guys have had an obsession with my rotation for the last 18 months... but it's for moments like this," the England head coach told reporters.
"We can bring in two people who know the system and the have utter belief and confidence in each other. It's a seamless transition.
"I said six months ago, we don't want to get to the quarter-finals and throw in young kids who are untested, so there has been a plan behind [the rotation]. It's for moments like this and I'm totally relaxed.
"I put my life on Leah and Abbie that, if called upon, they will be the best two players on the pitch."
On Bright, 25, he added: "She is in her room recovering.
"You're going to pick up bugs and, touch wood, we have not had any injuries and illness, apart from one or two. It's par for the course; it happens in life."
England need to beat Norway to stand any chance of qualifying a Great Britain team for the 2020 Olympics.
Only the top three European nations qualify, but seven of the eight quarter-finalists are from Europe, so if hosts France beat holders USA on Friday, England would need to repeat their third-placed finish in 2015 to seal a place at the Tokyo Games.
But Neville said his players would "embrace" the pressure.
The former Manchester United and Everton player said: "In the past, you'd probably shield the players from a fear of failure - but my girls don't have that.
"Three or four years ago we were crying out to get to these levels of attention and visibility. When we get here we're not going to back off and say it's a bit nerve-wracking.
"We are going to embrace it. You have an unbelievable set of human beings who are now exactly where they want to be, where they've dreamed of - and they won't back off. You will see that on the pitch.
"The bigger the occasion and the more pressure we've put them under, the more they've relaxed and the more they've played.
"It's the bigger games that my players like."
Neville said he "hasn't seen a better striker" at the World Cup
Neville also praised striker Ellen White, who has scored four goals in three games at the World Cup, saying she had developed from a "grafter" into a "predator" like former Manchester United and Netherlands striker Ruud van Nistelrooy.
The new Manchester City forward is in the race for the Golden Boot and sits one goal behind Australia's Sam Kerr and United states forward Alex Morgan.
Neville said the 30-year-old has benefited from staying closer to the goal, adding he "hadn't seen anyone better" at the World Cup.
"Ellen has taken her game to another level," he said. "At the European Championship two years ago, she played left-wing. People thought she was a grafter, a worker. Now she is one of the top centre-forwards at the tournament.
"We've said to her to save her energy for when the big moments come, when the ball drops in the box, and she has learned the hard way. For six months she looked at me as if I had a horn in my head because I'd tell her to stop running. She'd find herself at outside left or outside right.
"Now she is like a Van Nistelrooy, or an Alan Shearer, or a Michael Owen. She has turned from a hard-working grafter into a predator. That's been the biggest change.
"She's got that ruthless streak now where it's about goals, that's what I want my centre-forwards to do.
"Jodie Taylor has had it her whole career. She's a predator and now Ellen has added that little bit of killer instinct to her game."