Ridgers was injured in a first-half collision with a Belgian forward as he slid in to take the ball at East End Park.
The Tynecastle number two immediately looked in some distress and was carried off on a stretcher. The initial diagnosis from the Scotland medical staff was a knee injury but a scan will be needed in the coming days to determine the severity.
Tottenham goalkeeper Jordan Archer came on for Ridgers in the 42nd minute and was beaten by a clinical strike from Ziggy Badibanga.
With St Mirren's Grant Adam out with a leg fracture, Archer could be called on for the team's final two qualifiers for the UEFA Under-21 Championship against Luxembourg and Austria early next month as Billy Stark's side look to stay in the top two places and seal a play-off spot.
With Jordan Rhodes starting for the full international team against Australia tomorrow and Dundee United pair Gary Mackay-Steven and Johnny Russell injured, Stark was without the front three who started the previous match, a 2-2 qualifying draw in Bulgaria.
Rhodes has scored eight of the 11 goals in the qualifiers and Scotland lacked a cutting edge against a similarly well-organised Belgian outfit, who sit in third place in their section behind England and Norway with eight points from six games.
Bolton pair Michael O'Halloran and Gregg Wylde came in while Aberdeen's Peter Pawlett started on the right flank.
Stark handed a debut to Huddersfield defender Murray Wallace at centre-back.
Most of the first-half action took place in midfield with the visitors having slightly more possession but little penetration.
The only efforts of note were both deflected strikes. Stuart Armstrong saw his shot loop into the visiting goalkeeper's hands while Hannes van der Bruggen was closed down quickly as he shot from 22 yards and his effort was diverted wide as Ridgers rushed across goal.
Ridgers was hurt when he came off his line and slid in to intercept a through ball as Thomas Meunier raced through. The assistant referee immediately flagged for a free-kick to Scotland but there was no malice in the Belgian's challenge and he also needed treatment.
Scotland, with Stoke midfielder Jamie Ness on for Scott Allan, were looking the more assured side in the early stages of the second half but Archer was beaten in the 57th minute.
Anderlecht striker Badibanga took a short pass from Thorgan Hazard and spun away from Scotland's central defence before dispatching a left-footed shot into the bottom corner from 20 yards.
Hazard, who joined older brother Eden at Chelsea this summer from Lens, then won a free-kick 20 yards out following a mazy run.
The 19-year-old took the kick himself and curled the ball towards the bottom corner but Archer got down well to push the ball away.
Belgium were looking increasingly assured and Archer made another good stop from Dolly Menga's 25-yard strike.
However, the Scots did manage some late pressure. Belgian keeper Koen Catsell blocked a ball into the danger area from Celtic striker Tony Watt, who came off the bench for his debut, and Liam Kelly shot just wide from 30 yards in injury-time.