Scotland may face world champions New Zealand on Sunday without the services of injured lock Richie Gray.
The towering 23-year-old was withdrawn from Sale Sharks' victory over London Irish on Friday night with an ankle injury and faces a race against time to line up against the All Blacks at Murrayfield.
Gray was absent from Monday's training session and the Scottish Rugby Union subsequently confirmed that he "undertook an individual programme with the squad's medical team, following on from his ankle rehabilitation work over the last week."
With head coach Andy Robinson combating a host of front-row niggles, Glasgow Warriors prop Gordon Reid was drafted in to the sessions.
Scotland team manager Gavin Scott said: "We've asked Gordon to train with us today as Kyle Traynor played for his club, Bristol, yesterday and will thus follow our usual protocol and not be training with the squad today."
Robinson names his side on Tuesday and there will be at least four changes from the June victory over Samoa, with centre Joe Ansbro and scrum-half Chris Cusiter injured, prop Euan Murray unavailable and No 8 Richie Vernon discarded from the squad.