The Celtic Warriors skipper moved to full back for Wales at the Rugby World Cup after only four minutes of the Pool defeat against New Zealand following an injury to Garan Evans.
He made such a success of the job in that match that he was selected from the start for the quarter-final against the eventual champions England. All his previous caps for Wales had come at centre, where he has been figuring for his region this season, and on the wing.
"Gareth played full back in the last two test matches and did the job in both. He has a good boot when he uses it and offers us a lot of pace from the back," said Wales Coach, Steve Hansen.
Thomas will overtake Ieuan Evans as Wales's most capped threequarter against Scotland when he makes his seventy-third appearance. That leaves only Neil Jenkins (87) and Gareth Llewellyn, who will win his eighty-fourth cap in the same game, ahead of him in the Wales cap rankings. He will also be seeking the one try he needs to match Evans's Wales record tally of thirty-three.
"There's a big difference between this year's expectations and previous ones because we can justify this year's by looking at our performances in the Rugby World Cup. Before we had neither results nor good performances for justification," said Hansen. "We were beaten in Australia by two of the top teams in the world in England and New Zealand. Our performances would have been good enough to have beaten most other sides.
"Expectations in Wales are high but they are warranted and we need to look at that as a good thing not a bad thing. We know if we can perform to our highest standards, then eight times out of ten that's going to be good enough for us to win."
Hansen has made six changes to the team that went down 28-17 to England in the Rugby World Cup quarter-final in Brisbane three months ago. Duncan Jones and Sonny Parker return to the side after being unavailable because of injury.
Rhys Williams comes in for the injured Mark Jones. While up front Mefin Davies replaces the injured Robin McBryde and Gareth Llewellyn packs down in the second row in place of the injured Robert Sidoli. Martyn Williams is recalled to the back row at the expense of the unlucky Jonathan Thomas, who will undoubtedly figure in the match at some stage.
The other unlucky players from the English test are Iestyn Thomas and Mark Taylor, who have missed out not because of lack of form, but due to the quality of personnel available in their positions.
Also not considered for selection through injury were Craig Morgan, Garan Evans and Alix Popham. On the bench hookers Gareth Williams and Huw Bennett are bracketed together. A decision on who will play will be made tomorrow (Wed) after a fitness test for Williams.
"If it had been a game to secure the Grand Slam then maybe both Sidoli and McBryde could have played," added Hansen. "We have taken a long term approach with both of them. They should be back in contention for the Ireland game, but for the time being we are happy with the make up of the team.
"The key thing for us on this occasion was to let the players know where they stand so we can concentrate on our build up and ensure that we finish the week's training on a high."
New Scotland Coach, Matt Williams, is due to name his side at 1.00pm on Wednesday.