Arsenal midfielder Cesc Fabregas is set to be sidelined until April with a knee injury.
The Spaniard had to be substituted at half-time in Arsenal's 1-1 draw against Liverpool on Sunday following a challenge with Xabi Alonso.
The full extent of the damage has now been revealed, with Arsene Wenger confirming that he has a partial rupture of the medial knee ligament.
Fabregas had only recently returned to fitness following a problem with the same knee and he will now miss most of the rest of the season.
He will have to sit out a crucial period of the Premier League as well as Arsenal's UEFA Champions League tie against Roma.
Fabregas replaced William Gallas as Arsenal captain in November and Wenger admits it is a major blow to lose him.
"The news is not good because it is a partial rupture of the medial knee ligament that is taking us three to four months," Wenger said.
"We count four. He will be working hard to return earlier but we count four months.
"We will miss him of course but we have to find a way to compensate for the fact that he will not be on the pitch.
"I am sure we can deal with it and when he comes back he can help us to get over the line in the final months."