Inter have confirmed that Radja Nainggolan has suffered a thigh strain and said he would be "evaluated in the coming days".
Depending on the severity of the injury, Nainggolan is likely to miss Inter's forthcoming friendly matches against Zenit and Chelsea, and possibly subsequent friendlies as well.
Nainggolan suffered the injury in a pre-season game against FC Sion, with teammate Yann Karamoh also forced off as Inter endured a miserable afternoon, losing 2-0 in Switzerland.
“Radja Nainggolan and Yann Karamoh both underwent medical exmainations at the Istituto Clinico Humanitas in Rozzano,” the Nerazzurri confirmed on Friday.
“The Belgian midfielder has a strain to the rectus femoris muscle in his left thigh while the French forward has a slight strain to his right knee.
“Both players’ conditions will continue to be evaluated in the coming days.”
Nainggolan will definitely miss Inter's friendly against Zenit on Saturday before the Nerazzurri take part in the International Champions Cup. Inter face Chelsea in Nice on 28th July in their first match, before further games against Lyon in Lecce and Atletico Madrid in Madrid.
Although Nainggolan may now be rested for one or more of these fixtures, he has plenty of time to recover his fitness before the Serie A season starts on 19 August.
This injury caps a summer of mixed emotions for Nainggolan, who retired from international football after he was omitted from Roberto Martinez's Belgium squad for the World Cup.
He was also sorry to leave Roma after four years, but he was reunited with his former manager Luciano Spalletti at the San Siro.