Glasgow Warriors pair Peter Horne and Tim Swinson join Scotland's tour, replacing the injured Duncan Taylor and Jim Hamilton.
Taylor (calf) and Hamilton (ankle) were injured in Saturday's 24-6 win over USA in Houston, Texas, and will return home to continue their recovery with Saracens.
"This is obviously disappointing news for both these players who were keen to impress in the short time they had on this tour," said Scotland boss Vern Cotter.
"Everyone in the squad wishes them well and a quick recovery.
"It's now up to Peter [Horne] and Tim [Swinson] to continue the hard work put in by Duncan [Taylor] and Jim [Hamilton], and take advantage of this opportunity, as we prepare for another Test match."