London, Nov.5 Manchester United center back Rio Ferdinand's back injury has played up again, and he could be out of action for at least six weeks.

Ferdinand will miss Sunday's big Premier League clash at Chelsea.

The Sun quoted team mate Wes Brown, as saying: "He's been getting a lot of pain for a long time so he's sorting it out now."

"When he comes back he'll be a lot stronger. If you're not fit and want to play it's very hard. Believe me," he added. (ANI)