Belgium coach Marc Wilmots claims Chelsea's Eden Hazard could be out for up to a month while Manchester City captain Vincent Kompany will be absent for "six to eight weeks".
Wilmots was forced to omit both men from his squad for the international friendly against Portugal on March 29, along with fellow Premier League players Kevin De Bruyne and Jan Vertonghen.
Asked about Hazard, who has been struggling with a persistent hip problem, Wilmots said: "I have told Hazard to have some rest.
"We are not too worried about him. He has a muscle injury. He'll be out for three to four weeks."
Kompany limped out of City's 0-0 draw against Dynamo Kiev on Tuesday night with Manuel Pellegrini stating the centre-half will miss at least a month of action.
Wilmots predicts it will be longer and suggested the former Anderlecht and Hamburg defender will not be back until May.
"Vincent Kompany will be out for six to eight weeks," he added. "He has injured the other calf."
Bjorn Engels was handed a maiden call-up to the squad after impressing for Club Brugge this season with Thorgan Hazard and Guillaume Gillet recalled.
"He [Engels] is a boy with a good future," Wilmots said of the 21-year-old. "He takes the place of Kompany in the squad. Bjorn is doing very well and I want to see him in action."
On Thorgan Hazard, he added: "He is developing well. Maybe he's the one who is best placed to fill the position normally occupied by De Bruyne."