Courtney Lawes and Dylan Hartley are to undergo scans on their respective knee injuries as England coach Stuart Lancaster waits to discover if they will miss any of the autumn Tests.
The Northampton duo picked up their injuries in Saturday's Premiership defeat against Saracens and are doubtful for at least England's opening engagement against Fiji a week on Saturday, which is followed by Tests against Australia, South Africa and New Zealand.
On Sunday night Harlequins lock George Robson was added to the England squad as cover for Lawes, with London Irish hooker David Paice providing back-up for Hartley. Lancaster has also called Worcester prop Matt Mullan in as Quins loosehead Joe Marler nurses a tight hamstring.
The England coach will be concerned at the prospect of starting the autumn without two of his first-choice pack, particularly as Lawes missed a large part of last season with a left knee problem, although it is his right that is troubling him on this occasion.
Lawes and Hartley will have their scans this evening, with the results being made public when Lancaster speaks to the media on Tuesday evening.
An RFU statement read: "Courtney Lawes and Dylan Hartley of Northampton Saints will this evening have scans on knee injuries and a further update on their progress will be given at Stuart Lancaster's 5pm briefing tomorrow."