Kompany missed training for the second straight day on Friday while he gets attention to a groin strain picked up late in Tuesday's 2-1 win over Algeria. (Agencies)
"Vincent felt something in the final few minutes and was not able to sprint 100 percent," said Belgium coach Marc Wilmots.
"He hoped that resting it overnight would resolve the problem, but it wasn't the case and on Wednesday morning he still had pain in the left groin,” he added.
"We decided he would work alone from the rest of the squad for two days with the physiotherapist Lieven Maesschalk and the medical staff. All being well, he will be back training with the rest of the squad on Saturday,” he said.
Kompany's importance to the team goes well beyond his accomplished performances at centre half, given he is the well-established leader and defensive organiser.
Should the Manchester City defender not make it then Wilmots would have to turn to Thomas Vermaelen, Laurent Ciman or Nicolas Lombaerts as cover.
Russia drew 1-1 with South Korea in their opening game and coach Fabio Capello is likely to stick with goalkeeper Igor Akinfeev despite his blunder in that game.
Akinfeev let a long range Lee Keun-ho shot slip through his body to gift the lead to the Koreans.
"Just like some players can miss penalties it can happen that a keeper makes a mistake as well," said Capello.
"You can accept a mistake from a great keeper like Akinfeev. It turned out fine as we were able to make up the difference. I'm very happy with Akinfeev," he said.
Capello, who turned 68 on Wednesday, said he hoped to see his side pick up where they left off with their second half performance against the Koreans.
"The way our team played at the end of the second half was the best possible birthday present they could have given me,” Capello said.
"This team has the willpower, they can play at the top level. At halftime I asked the players to act more confidently and show their best qualities. The players followed my words, that's the most important thing," he added.
Kompany missed training for the second straight day on Friday while he gets attention to a groin strain picked up late in Tuesday's 2-1 win over Algeria.