London - England's fitness problems ahead of the Six Nations intensified Tuesday after prop Kyle Sinckler had to leave the squad's training camp in Portugal.
The Harlequins front-row arrived in Villamoura on Monday with a potential hamstring strain and has now been replaced by Bath's Henry Thomas.
"Kyle will undergo further assessment and treatment with his club Harlequins this week," said a statement issued by England's governing Rugby Football Union.
Exeter's Harry Williams is now the next in line to provide cover for Dan Cole, set to be England's first-choice tighthead prop when they begin their Six Nations title defence against Italy in Rome's Olympic Stadium a week on Sunday.
Sinckler, 24, emerged as a promising Test player during the British and Irish Lions drawn series in New Zealand last year but his career has since taken a turn for the worse, including a seven-week ban for gouging in October.
"Now is the test for him -- how much he really wants it -- otherwise he's going to become a pantomime character," said England coach Eddie Jones last week.
"He has got to show he really wants to be a Test prop and we are going to back him a hundred percent and give him every opportunity because he's a good kid. I'm going to back him to come through."
England have been badly hit at prop amid a number of injuries prior to the Six Nations, with looseheads Joe Marler, Matt Mullan, Ellis Genge and Beno Obano all set to miss at least part of the tournament.
In all, they are missing 15 players as things stand with back Henry Slade (shoulder) joining an injury list that already included wing Elliot Daly and back-row forwards Nathan Hughes and Billy Vunipola.