Ross Stewart of Sunderland and Craig Halkett of Hearts were called up to the Scotland squad for the first time.
Johnstone goalkeeper Zander Clark will also join the team to replace the injured David Marshall.
Stewart has scored 22 goals in 38 league games this season.
Halkett will cover the center of defense after the departure of Scott McKenna, while Liam Cooper and John Suttar remained on the sidelines.
Both new challenges could make their debut in a friendly against Poland on Thursday, with Scotland playing either Austria or Wales next Tuesday.
Meanwhile, captain Andy Robertson is in doubt after missing Liverpool’s quarter-final win over Nottingham Forest in the FA Cup due to illness.
Stewart played for Ayrshire youth clubs Ardir Thistle and Kilwinning Rangers after several years in the professional youth system with St Mirren, Celtic and Partick Thistle.
He then returned to senior play with Albion Rovers and played for St Mirren and Alloa Athletic before rising to fame at Ross County where he scored 28 goals in 82 games and earned a move to the South.
Halkett was a key member of the Hearts back three that performed well helping Tynecastle to third place in the Scottish Premier League.
Scotland will play the Poles instead of the postponed World Cup play-off semi-final against Ukraine.
The game will be played in Hampden and £10 of each ticket sold will go towards UNICEF’s response to Ukraine following Russia’s invasion of the country.
The Football Association of Scotland has announced that 25,000 tickets have already been sold for the match.
“We have been both heartened and humbled by the response from the Scottish fans and we thank everyone who has already bought a ticket,” said SFA Chief Executive Ian Maxwell.
Poland was supposed to play the Russians on March 24, but on March 29 they were given the chance to play the Czech Republic or Sweden in the final.
Scotland and Ukraine hope to meet in June, with the winners playing either Wales or Austria.
The two teams will meet in Cardiff on Thursday, with the losers hosting Scotland in a friendly match on 29 March.
Scotland national team
Goalkeepers: Craig Gordon (Hearts), Liam Kelly (Motherwell), Zander Clarke (St Johnstone).
Defenders: Grant Hanley (Norwich City), Jack Hendry (Club Brugge), Craig Halkett (Hearts), Aaron Hickey (Bologna), Stephen O’Donnell (Motherwell), Nathan Patterson (Everton) Andy Robertson (Liverpool), Greg Taylor (Celtic). Kieran Tierney (Arsenal)
Midfielders: Stuart Armstrong (Southampton), Lewis Ferguson (Aberdeen), Billy Gilmour (Norwich, on loan from Chelsea), Ryan Jack (Rangers), John McGinn (Aston Villa), Callum McGregor (Celtic), Kenny McLean (Norwich), Scott McTominay. (Manchester United).
Forwards: Che Adams (Southampton), Jacob Brown (Stoke), Ryan Christie (Bournemouth), Ross Stewart (Sunderland).