Dele Alli will not take part in England training on Thursday afternoon as he is still being monitored by the Three Lions' medical team.
The Three Lions face Panama in their second game of Group G, knowing a victory will be enough to see them through to the Round of 16 for the first time since 2010.
Alli started for England in their opening 2-1 victory over Tunisia in Volgograd on Monday when he looked set to come off in the first half after suffering a knock. Fabian Delph was stripped and seemingly ready to come on, but Alli managed 80 minutes before eventually being replaced.
The England midfielder went for a scan as his team-mates trained on Tuesday afternoon and the FA has confirmed the assessment showed a minor thigh strain that will need managing over the coming days.
But now they have pulled him from training as a precaution and he will continue to be monitored by England's medical staff in the build-up to the Panama game.
In a tweet, England said: "The Three Lions will be back on the training field shortly, as we begin our build-up for Sunday’s game again Panama.
Dele Alli is the only absentee from the session, as he continues his recovery from a slight thigh strain."
After the game on Monday, Alli said of his injury: "Hopefully I am okay. It's my quad."
One of Marcus Rashford or Ruben Loftus-Cheek, who both impressed when they came on against Tunisia, could start in his place, with Gareth Southgate confirming he was assessing his options earlier this week.
"We had to keep monitoring Dele," the Three Lions boss said on Monday. "He was feeling a little bit of an issue just before half-time, but he felt he could carry on and I thought the runs that he was making and the way he was pressing the ball was still causing a problem.
"But we have good options on the bench and we felt to put the freshness of Marcus (Rashford) and Ruben (Loftus-Cheek) would both bring fresh energy but also a different sort of threat to the one that we'd posed."
