Chelsea midfielder Ramires will be out for up to four weeks with a knee injury, the Premier League club said on Sunday.
The Brazilian was injured during his side's FA Cup victory at Queens Park Rangers on Saturday and scans revealed ligament damage.
"Scans confirm Ramires suffered a medial ligament injury to his right knee in Saturday's game against Queens Park Rangers," the club said on its website.
"He is expected to be out for three to four weeks."
Ramires has been one of the most impressive performers in a difficult season for Chelsea, making 19 league starts and contributing four goals.
He is set to miss the Premier League match against Manchester United at Stamford Bridge on February 5, as well as fixtures at Swansea and Everton - plus an FA Cup tie at home to Birmingham City.
He will also be a doubt for the first leg of the Champions League last-16 tie against Napoli.