Arsenal manager Arsene Wenger says extending Per Mertesacker's contract was a very easy decision.
The former Germany international has signed a one-year contract extension.
He is yet to make his debut for the club this season after suffering a serious knee injury but has resumed training and is expected to be back in March.
"He is a leader of the team and he is also one of the four centre backs who has experience and can guide the team," Wenger told Arsenal's official website.
"There were no negotiations in fact, because he had an option for extension. So it's not really a new contract, it's just an extension of the old one. We had to take that option early in the season and the decision was made quite easily.
"On the pitch he has his own technical attributes, that is his reading of the game, his intelligence, his guidance. He's good in the air because of his size.
"Mentally, he's a guy who brings a level of urgency into the team, a level of focus, a level of desire to do well and he's very demanding with the people around him. He's very respected as well and that's why he gets a lot from the players around him.
"I've never seen a training session where Per was not fully focused to do well. That's why he has improved with us a lot
