British and Irish Lions loosehead prop Alex Coribisiero is a doubt for England's clash with New Zealand at Twickenham on Saturday.
The Northampton Saints front-row, who is still struggling with knee problems, is to undergo a crucial training session on Tuesday that will go some way to deciding whether he participates in the key November Test fixture.
This news leaves England desperately short of looseheads, with Mako Vunipola ruled out through a knee injury and Joe Marler following return to play protocols for concussion.
London Wasps' Matt Mullan has been called up to the squad, and could face something of a baptism of fire on what would be only his second cap.
"We're monitoring Alex now. He's normally a one session per game player, especially on a Tuesday when we do two heavy sessions," forwards coach Graham Rowntree told Sky Sports.
"We're currently monitoring him to see what he's able to do this afternoon, as we are with a couple of other players.
"We'll know more after we've monitored him this afternoon. As far as I'm concerned we're still as we are for the weekend."
Corbisiero saw his knee specialist in a routine meeting on Monday, but Rowntree was keen to stress that did not represent anything unusual.
"Seeing a specialist is part of Alex's ongoing situation with his knee. A lot of our players are seeing specialists all the time," revealed Rowntree.
"It's nothing out of the ordinary, it's part of his knee management in conjunction with Northampton and our team physios."