With both Finn Russell and Adam Hastings unavailable for the game at Murrayfield due to club commitments, the coach will choose between Blair Kinghorn and Ross Thompson as his starting 10, even though both are untested in that position at international level.
Townsend has confirmed that he now sees Kinghorn as a stand-off rather than a full-back or winger, the positions in which the Edinburgh man won his 25 caps.
Kinghorn played at 10 for his club at the end of last season under Richard Cockerill and was selected again at fly-half by his successor, Mike Blair, for Edinburgh’s opening game of the new campaign against the Scarlets.
He impressed in the 26-22 win but injured his quad and has not played since. Townsend says he is fit again - he trained with Scotland on Monday - and could come into contention for Edinburgh’s game on Saturday against Zebre Parma.
The national coach, who has named a 42-man autumn squad which includes Scotland’s eight Lions, said it was a straight fight between Kinghorn and the uncapped Glasgow Warriors stand-off Thompson for the No 10 jersey to face Tonga on October 30.
Thompson, 22, made his Glasgow debut in January and has been mainstay in the side since, playing with an assurance that belies his lack of experience.
“Ross had a great season and both he and Blair were going to be involved in the summer covering 10,” said Townsend, referring to Scotland’s east European tour which had to be abandoned due to Covid issues.
“We wanted to give Ross another opportunity. I think he started this season just as well as he finished the last one, but we see Blair as a 10. Particularly at the beginning of this campaign he will be competing with Ross for that position and when Finn and Adam come in Blair and Ross will be in the mix for 10.
“We know that Blair can play other positions and has played very well at Test level on the wing and at full-back. I’ve been delighted by his progress at Edinburgh. He is very engaged in playing 10 and he takes a leadership role in attack and I think he has huge potential there.
“We are in a really good position that we can leave out two experienced 10s - Duncan Weir and Jaco van der Walt, who has now picked up an injury. Both are playing well but we have brought in two players who we think can thrive in this environment and have much more to bring in their games in the future.”
Thompson is one of five of uncapped Glasgow players called up by Townsend after a bright start to the season which has seen the club win three of their four United Rugby Championship matches.
The stand-off is joined by winger Rufus McLean, flanker Rory Darge, centre Sione Tuipulotu and scrum-half Jamie Dobie but there is no place for full-back Cole Forbes who has been cut from the training squad announced last week along with the young Edinburgh trio Jack Blain, Matt Currie and Charlie Savala.
The capital club does supply four uncapped players in locks Jamie Hodgson and Marshall Sykes, flanker Luke Crosbie and South Africa-born prop Pierre Schoeman, who qualified for Scotland in the summer after fulfilling the three-year residency requirement.
As expected Dylan Richardson, another South African, is included, with Townsend revealing that the 22-year-old openside has been on Scotland’s radar for four years.
The Cell C Sharks back row, who qualifies through his Edinburgh-born father, impressed in the summer against the British & Irish Lions.
“We’ve known about Dylan since he was 18,” said Townsend. “His dad had got in contact, or we had got in contact with his dad, a number of years ago and we’ve been aware he’s Scottish qualified since then.
“He played really well for South Africa at the U20 World Championship two years ago. He was a hooker who was playing in the back row then but he has decided to go for the back row as his No 1 position.
“We saw how well he played for the Sharks in their various competitions and also against the Lions. He played twice in a week against the Lions and we were really impressed by him.
“There were conversations around ‘would you commit to Scotland?’ He’s got the heritage link and over the last few weeks he’s made that commitment.”
South Africa are among Scotland’s autumn opponents and will visit Murrayfield on November 13, six days after Australia are due in Edinburgh. Both games are sold out. The series concludes against Japan at Murrayfield on November 20.
While the English-based players (and Paris-based Russell) will miss the Tonga match, they will be available for the other three which will see the squad bolstered by the likes of Stuart Hogg, Duhan van der Merwe, Rory Sutherland, Chris Harris, Huw Jones and Sam Skinner, as well as Russell and Hastings. There are also places for Leicester’s Matt Scott, who has not played for Scotland for four years, and Bath back-row Josh Bayliss and Sale hooker Ewan Ashman, both of whom are uncapped.
There are notable omissions and Townsend admitted it had been a tough decision to leave out scrum-halves Ben Vellacott and Scott Steele but he has stuck with the Glasgow Warriors trio of Ali Price, George Horne and Dobie.
Other high-profile absentees include WP Nel, Richie Gray, Sean Maitland and Ryan Wilson.
A number of players were unavailable due to injury, and the second row was particularly badly hit with Jonny Gray, Scott Cummings, Alex Craig, Glen Young, Ben Toolis and Cameron Henderson all ruled out. Joining them on the treatment table are Simon Berghan, Cam Redpath, Duncan Taylor and James Lang.