Arsenal midfielder Santi Cazorla will require surgery on his injured ankle and has been ruled out for the next three months.
The Spaniard injured the plantaris tendon in his right foot during a Champions League tie in October, and has not featured for the north Londoners since.
On Wednesday, Gunners boss Arsene Wenger said Cazorla's return was only delayed by inflammation and that there were now further "setbacks", with confirmation that the 31-year-old will have to go under the knife before continuing his rehabilitation.
Wenger's side have won four, drawn four and lost one across all competitions in Cazorla's absence, and find themselves sitting fourth in the Premier League table.
— Arsenal FC (@Arsenal) December 1, 2016
After originally joining the Gunners as a versatile winger, Cazorla has been their best midfielder in recent times and became key to how they play, as Wenger explained last week.
"Santi is important to our technical stability in the team, to the quality of our decision-making and to our build-up from deep midfield to the high midfield," the Frenchman told reporters.
"That is an important stage because it gets the ball out from the defenders. Santi is a massive player for us.
"But we have enough quality players in our side to get around that. We are good enough to find solutions despite the fact he is not there."