Steve Clarke spoke about "evolution not revolution" ahead of Scotland's Nations League opener against Poland at Hampden Park on Thursday night.
The Scottish squad got together for the first time since the dismal performance in the 2024 European Championship where they failed to get out of their group in Germany with only one point from three games.
The absence of long-term injured players such as Kieran Tierney, Nathan Patterson and Aaron Hickey was compounded when Kilmarnock goalkeeper Robby McCrorie, Torino striker Che Adams and Celtic pair James Forrest and Greg Taylor all left the original squad for the Group A game against the Poles and the trip to Portugal on Sunday.
Vancouver Whitecaps' Ryan Gauld had been called into the squad after a 10-year absence along with fellow uncapped duo, Sturm Graz full-back Max Johnston and attacker Ben Doakes, who is on loan at Middlesbrough from Liverpool.
They were joined by Rangers midfielder Connor Barron, Dundee goalkeeper Jon McCracken and Sassuolo left-back Josh Doig, making it six potential debutants.
"It's evolution, not revolution," said Clarke, who confirmed that Adams would miss the game through injury after reports claimed the player was fit and had asked for time to settle in at his new club in Italy.
"Obviously, this time, we have a significant number of injuries.
"That has probably impacted my squad selection a little bit, which means I've had to dip down into Scot Gemmill's under-21 squad, probably too many times if I'm being honest because the under-21s also have a couple of very important fixtures coming up, but that brings its own freshness.
"It's important that we respect the core group that have managed to qualify for back-to-back European tournaments.
"But then within that core group, you have to try and add a little bit more and hopefully we can add something that makes us better.
"It's not going to happen overnight.
"It's not going to happen across the two games that we're going to play now, but I'm looking at this campaign in the Nations League and thinking, this is the chance to try and evolve these group so when we do get to the World Cup qualifiers, we're in a better shape, ready to go again and ready to qualify for the third tournament out of four."
However, Clarke is aware that a chance to become the first Scotland team to make it out of a group stage at a major tournament was spurned in Germany as he looked to find a way to overcome the sort of quality he would face in the Nations League, where Croatia make up the group.
The former West Brom and Kilmarnock boss added: "You get there the first time, we didn't do what we wanted to do. You get there the second time, we didn't do what we wanted to do.
"So you have to keep looking to get there and you have to target the glass ceiling – no Scottish team's ever done it.
"Probably a little bit more quality (needed) when we get to that level, when you play against opponents of the level we played against in the summer, when we play against the opponents of the level that we're going to play against now in the Nations League.
"So slowly, slowly, trying to find a formula that will break the glass ceiling."
On the absence of Adams, Clarke added: "The club informed us on Saturday morning that he picked up a knock in the game. The conversation we share then is, does he come across to be assessed and sent back to Italy? There was no point, that's why he misses out.
"By the same token, the two Celtic boys who played at the weekend came in on Sunday, get assessed by our medics and sent home because it's easy, they're in Glasgow. No big drama on that one."
