Leeds United captain Liam Cooper will vie for a place in the heart of the Scotland defence with Grant Hanley, Christophe Berra and Charlie Mulgrew
Scotland manager Gordon Strachan has called up Leeds United centre-half Liam Cooper to his squad for next month's games against Slovakia and Slovenia.
"He's playing well in a winning team and is a big influence, so he deserves to be there," Strachan said of Cooper, 26, ahead of the World Cup qualifiers.
Russell Martin and Steven Naismith, neither of whom are starting games for Norwich City, have been omitted.
Scotland must win both matches to have a realistic chance of the play-offs.
United skipper Cooper was first included in a Scotland squad in March 2016 ahead of a match against Denmark but has yet to win his first full cap.
Scotland, 43rd in the Fifa world rankings, host Slovakia, ranked 19th, on Thursday 5 October.
Three days later they conclude the group matches of the campaign against Slovenia in Ljubljana.
With two games remaining, England top Group F on 20 points, ahead of Slovakia on 15. Slovenia, ranked 55th by Fifa, are ahead of fourth-placed Scotland on goal difference.
Eight of the nine group runners-up will contest a two-legged play-off to secure a place at the World Cup in Russia next year.
Scotland squad for World Cup qualifiers against Slovakia and Slovenia
Goalkeepers: Jordan Archer (Millwall), Craig Gordon (Celtic), Allan McGregor (Hull City)
Defenders: Ikechi Anya (Derby County), Christophe Berra (Heart of Midlothian), Grant Hanley (Norwich City), Liam Cooper (Leeds United), Charlie Mulgrew (Blackburn Rovers), Andrew Robertson (Liverpool), Kieran Tierney (Celtic), Steven Whittaker (Hibernian)
Midfielders: Stuart Armstrong (Celtic), Barry Bannan (Sheffield Wednesday), Scott Brown (Celtic), Darren Fletcher (Stoke City), Ryan Fraser (Bournemouth), James Forrest (Celtic), James McArthur (Crystal Palace), John McGinn (Hibernian), Matt Phillips (West Bromwich Albion), Matt Ritchie (Newcastle United), Robert Snodgrass (Aston Villa)*
Forwards: Steven Fletcher (Sheffield Wednesday), Leigh Griffiths (Celtic), Chris Martin (Derby County)
*On loan from West Ham United
Source: bbc.com