Steve Clarke believes Scotland can "change the mood about the place" with a positive result against Portugal in the Nations League on Tuesday.
The Scots are winless in their last nine competitive games and fell to a defeat against Croatia in Zagreb after what would have been a late equaliser was ruled out for offside following a VAR check.
They return to Hampden Park on Tuesday to take on Portugal as they look for their first victory in Group A1.
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Cristiano Ronaldo netted the late winner when the sides met in Lisbon in September, while Scotland had already lost to Poland by a one-goal margin in their group opener in Glasgow.
Rangers midfielder Connor Barron is the latest call-up to the squad with Celtic's James Forrest withdrawing injured.
Despite the disappointing start and a number of regulars unavailable, Clarke insists his players are confident of taking something against Roberto Martinez's side.
"They do believe in themselves," Clarke said.
"The players understand we're playing difficult opponents, they understand the squad could be stronger.
"I don't speak about it too much because I think it's disrespectful to the boys that are in the squad. We have to concentrate on who we have here.
"We have to go out against Portugal and be good at everything in the game, to go out and get the result that might just change the mood about the place."
He added: "After 20 years in the international wilderness, this group of players have been to two major tournaments.
"They've got promotion to the top level of this Nations League. I don't understand why people would be doubting this group.
"It's a tough moment, no doubt about it. But we believe in ourselves."
Scotland squad in full
Goalkeepers: Craig Gordon (Hearts), Jon McCracken (Dundee), Robby McCrorie (Kilmarnock)
Defenders: Nicky Devlin (Aberdeen), Grant Hanley (Norwich), Liam Lindsay (Preston North End), Ryan Porteous (Watford), Anthony Ralston (Celtic), Andrew Robertson (Liverpool), John Souttar (Rangers), Jack McKenzie (Aberdeen)
Midfielders: Ryan Christie (Bournemouth), Ben Doak (Middlesbrough), Ryan Gauld (Vancouver Whitecaps), Billy Gilmour (Napoli), Andy Irving (West Ham), Kenny McLean (Norwich), Scott McTominay (Napoli), Lewis Morgan (New York Red Bulls), Connor Barron (Rangers)
Forwards: Ché Adams (Torino), Lyndon Dykes (Birmingham City), Kevin Nisbet (Aberdeen)
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