Arsenal's Laurent Koscielny is the best defender in the Premier League, according to former England and Manchester United centre-back Rio Ferdinand.
Ferdinand also praised the Gunners backline in Wednesday's impressive 3-0 Champions League win over Greek champions Olympiakos Piraeus, which sealed their progress to the knockout stages for a 16th consecutive year.
"Laurent Koscielny, when he's on form, he's the best defender in the league for me. He's one of those you don't want to play against -- he's quick, he's aggressive," Ferdinand was quoted as saying by British media.
"You need a platform at the back, you need intensity. They showed a few things today -- composure, focus, and management of the game. They've got to show this more often, that must be the really frustrating thing for Arsene Wenger."
Ferdinand feels Arsenal needs a combative midfielder and has urged manager Wenger to dip into the transfer market to fill the void.
"I think they need some more cover in the central defensive area. They need a dominant central midfielder. It's not been the same since Patrick Vieira left," Ferdinand added.
Former captain Vieira left the club in 2005.
Arsenal will hope to leapfrog surprise leaders Leicester City, who host champions Chelsea on Monday, in the Premier League when they travel to take on bottom side Aston Villa the previous day.