Lazio will be without goalkeeper Federico Marchetti and striker Helder Postiga for their final two Serie A games of the season.
Both players sustained injuries in training at the weekend and sat out Monday's 3-3 draw against Hellas Verona.
Marchetti is sidelined with a groin injury while Portugal forward Postiga sustained a knee injury.
"The Portuguese player has suffered a lesion to his medial collateral ligament in a knee," Lazio team doctor Stefano Salvatori said to Lazio Radio.
"It's not a serious injury but Postiga's season is over.
"We, alongside the medical staff of the Portuguese national team, will help him to recover in view of the World Cup."
The 31-year-old Postiga, who joined Lazio from Valencia on loan in January, is expected to be included in Paulo Bento's squad for this summer's top tournament in Brazil.
Lazio are 10th in the standings and travel to the San Siro to face Inter Milan on Saturday before ending the campaign at home to Bologna on May 18.