Hibernian defender Paul Hanlon has been added to the Scotland squad for Wednesday's Nations League meeting with Czech Republic at Hampden.
The 30-year-old left-sided centre-half is called up with captain Andy Robertson and Liam Cooper unavailable.
Robertson is suspended after his yellow card in Sunday's 1-0 win over Slovakia, a game Cooper missed through injury.
Defenders Scott McKenna, Liam Palmer and Kieran Tierney withdrew from Steve Clarke's pool of players last week.
McKenna and Palmer have injuries, while Tierney was instructed to self-isolate following a positive Covid-19 test for Stuart Armstrong.
Hanlon, who missed Saturday's League Cup win over Cove Rangers with an injury, joins up with Easter Road team-mates Ryan Porteous and Paul McGinn in the squad, with all three uncapped.
More Covid call-offs for Czechs
Meanwhile, the Czech Republic have lost head coach Jaroslav Silhavy and an unnamed player for Wednesday's game in Glasgow after the pair tested positive on Monday.
Four new players - midfielders Tomas Malinsky and Michal Sacek and strikers Tomas Poznar and Michael Rabusic - have been added to the visitors' travelling party and assistant coach Jiri Chytry will take charge.
The Czechs, who had to assemble an entirely new squad at short notice for last month's 2-1 defeat to Scotland in Olomouc, had five Covid-related withdrawals prior to Sunday's win in Israel, including captain Borek Dockal.
After three matches, Scotland lead Czech Republic by one point in Group B2.