Scotland wing Sean Lamont has been ruled out of Saturday's Calcutta Cup meeting with England, while Peter Horne and Ross Ford are injury doubts.
Sean Maitland has been called up as a replacement for Glasgow team-mate Lamont, who sustained a knee injury on club duty against Zebre on Friday.
Fly-half Horne is being assessed after suffering concussion in the same match.
Edinburgh hooker Stuart McInally has been called up as cover for club-mate Ford, who has a back problem.
Horne, who is primarily an inside centre but who started at fly-half in the 22-19 defeat by Italy after Finn Russell's suspension and injuries to Duncan Weir and Ruaridh Jackson, is a doubt for the Six Nations trip to Twickenham, where Scotland have not won since 1983.
Horne is expected to begin his graduated return to play protocol on Monday.
British & Irish Lions wing Maitland, who can also play at full-back, was himself recovering from a shoulder injury picked up in January before being called up to replace Lamont, who will miss the rest of the Six Nations.
Uncapped McInally receives his "precautionary" call despite having only just made his first start at hooker for Edinburgh, in Saturday's 29-8 win over Treviso.
He was an unused replacement for Scotland against South Africa in 2012 before making the decision to switch from number eight to the front row.
McInally played in that position while on loan to Bristol last year before returning to the Pro12.