The two players got hurt in Lazio's 2-0 triumph over Sampdoria at the weekend.
A statement from the club read: "Tests done on Alvaro Gonzalez have revealed a first degree lesion on his right calf.
"Miroslav Klose has a first degree muscular injury in his left thigh. The expected recovery period for the two players is four weeks."
Both players will sit out the Serie A games against Napoli, Torino, Livorno and Hellas Verona.
Klose is Lazio's second top scorer with seven goals this season.
Lazio, coached by Edy Reja, are seventh in the standings, two points behind Inter Milan, who are fifth hold the last Europa League qualifying spot with six games remaining.