Roma striker Luca Toni will be out for at least six weeks after suffering a calf injury during Saturday's 2-1 win over Juventus.
The Italy international, who is on loan from Bayern Munich, joined Claudio Ranieri's side earlier this month, but will now miss the next nine matches after tests revealed the extent of the damage.
"I am really annoyed that I have to stop now," Toni said.
"But when I return to play I will be even more determined than before."
The 32-year-old has struck two goals in four league appearances for Roma since his arrival from Bayern.