Hugh Blake will make his Scotland debut at flanker this weekend when they face Ireland in Dublin, with Ruaridh Jackson at full-back.
After his December arrival, Blake was an unused squad member during the 2015 Six Nations, but impressed for Edinburgh and Scotland 7s before joining Glasgow.
His Glasgow Warriors team-mate Mike Cusack (prop) could also make his debut from the bench.
The Ireland Test is the first in a four-match schedule to be played on consecutive Saturdays, as the extended Scotland 47-man squad gear up for the Rugby World Cup.
The Scotland team will then announce the final 31-man squad for the Rugby World Cup before concluding preparations against France in Paris on Saturday, September 5.
Head Coach Vern Cotter, said: "It's been important to get a good look at everyone over the last two months.
"The strength and conditioning team have worked hard to get more power and endurance from our players, while we've also focused a lot on basic skill sets.
"The successful application of these elements will enable us to perform the various forms of rugby that we would like to play; dominating collisions and using these skill sets to become better at making and executing decisions.
"These 23 players now have the first chance to stake a claim for the final 31-man squad for the Rugby World Cup, against what we know is quality opposition.”
Scrum-half Henry Pyrgos will start as captain for the first time alongside stand-off Greig Tonks, who will make his first start for his country since switching from his once favoured full-back position at the start of the 2014/15 season.
Peter Horne will reform the Pro12 winning centre partnership with fellow Warrior Richie Vernon, who makes his first appearance for Scotland since transforming from a number eight two years ago.
The backs are completed by Sean Lamont, Tim Visser and Ruaridh Jackson, the latter set to make a second appearance at full-back for the national team, the first coming as a replacement in the victory over USA in Houston last year.
In the pack, a stomach bug has prevented Stuart McInally from making is debut alongside props Ryan Grant and Jon Welsh, meaning Fraser Brown starts with Ross Ford coming into the squad on the bench.
Jim Hamilton and Grant Gilchrist are behind them in the boiler house; the latter set for his first appearance since captaining Scotland last summer having missed the majority of the 2014/15 season with an arm injury.
Finally, in the back-row, Blake is joined by Blair Cowan on the blindside flank, and David Denton at number eight.
On the bench, forwards Ross Ford, Gordon Reid, Cusack, Rob Harley and John Barclay join backs Sam Hidalgo-Clyne, Duncan Weir and Matt Scott, with Scott a replacement for Tommy Seymour who sprained his hip in training.
Scotland: 15 Ruaridh Jackson, 14 Sean Lamont, 13 Richie Vernon, 12 Peter Horne, 11 Tim Visser, 10 Greig Tonks, 9 Henry Prygos (c), 8 David Denton, 7 Hugh Blake, 6 Blair Cowan, 5 Grant Gilchrist, 4 Jim Hamilton, 3 Jon Welsh, 2 Fraser Brown, 1 Ryan Grant
Replacements: 16 Ross Ford, 17 Gordon Reid, 18 Mike Cusack, 19 Rob Harley, 20 John Barclay, 21 Sam Hidalgo-Clyne, 22 Duncan Weir, 23 Matt Scott
Date: Saturday, August 15
Venue: Aviva Stadium, Dublin
Kick-off: 17:00 local (16:00 GMT)
Referee: Pascal Gauzère (France)
Assistant Referees: Jérôme Garcès (France), Marius Mitrea (Italy)
TMO: Graham Hughes (England)