Arsenal manager Arsene Wenger has confirmed that defender Per Mertesacker will be out for "months" after suffering a knee injury.
The former Germany international underwent surgery on Tuesday after suffering the injury last week against Lens.
The Frenchman confirmed that a new experienced defender will be signed to fill the void left by the 31-year-old.
"We have bad news on Per Mertesacker," Wenger told reporters.
"He played in Lens on Friday night, he finished the game and had a little pain on his knee. We found out the next day that it was much more serious than expected.
"He had surgery yesterday in Germany. It all went well. I know you will ask me for how long he will be out. I don’t know that, it’s [some] months, but I don’t know [exactly] how long he will be out for.
"We have to look for an option to get a bit more experience.
"We will see some of our young centre backs on Thursday as well.
"With Per being out, we are a bit short on the experience front and we are looking to bring somebody in."
