Uncapped Northampton centre Joe Ansbro will replace the injured Max Evans in Scotland's team to meet South Africa in the second autumn Test at Murrayfield on Saturday.
Evans has not sufficiently recovered from the shoulder injury he suffered at the end of last Saturday's 49-3 loss to New Zealand.
Ansbro had been named in the Scotland A team for Friday night's match with the United States, but has now been promoted to the first XV and will make his debut against the world champions.
Ansbro told Scotland's official website: "It's the highlight of my rugby career so far to be called up for a game of this magnitude to represent Scotland.
"There's excitement, pride and a bit of nerves as well, a good mix really."
Ansbro's inclusion takes the number of changes made in head coach Andy Robinson's starting XV to five, with one positional switch.
He joins captain Rory Lawson, Scott MacLeod, Nathan Hines and Nikki Walker in being promoted to the starting line-up, with Kelly Brown switching from blindside flanker to number eight.
Robinson added: "Joe is a talented footballer. We have been monitoring his progress at Northampton closely and he has been getting regular game time this season.
"We took him with Scotland A to the IRB Nations Cup in Romania in 2009 and we believe he has the required qualities to perform in international rugby."
The Scotland medical team reported Evans' condition is improving all the time and he could be included in next weekend's third and final autumn international against Samoa in Aberdeen.