Arsenal defender David Luiz faces a spell on the sidelines because of a knee injury that may require surgery, manager Mikel Arteta said.
The 33-year-old Brazilian played all 90 minutes of a 3-3 draw with West Ham United before the international break, but missed Saturday's 3-0 home defeat by Liverpool after discomfort in his right knee.
"There are a few possibilities - being a little bit more conservative on the treatment, or having to go through surgery," Arteta said.
"We are talking with the doctors right now to make the right decision on that, but looks like he will be out for a few weeks at least.
"It depends on what decision we will take. If it's more conservative it will be short-term, if it's a little bit more radical what he needs, obviously it will take longer."
Luiz, who is in the final year of his Arsenal contract, has made 29 appearances in all competitions this season.
Arteta also said full back Kieran Tierney, who was forced off with a knee problem just before half-time against the Premier League champions, is a doubt for the first leg of the Europa League quarter-final against Slavia Prague on Thursday.
"He felt something in his knee and he was in pain so it looks like he will be injured, but we don't know for how long," the Spanish coach added.