Roy Keane has warned his former Manchester United team mate Wayne Rooney he has "achieved nothing" in football yet.

The ex-Manchester United captain, now manager of Sunderland, claims Rooney still has a lot to do before he can be judged one of the great players of his generation.

"For me, the jury's still out on Wayne," said Keane. "I think he's got a hell of a lot to do. Wayne has achieved nothing - and would probably say that himself. I would judge players over a few years rather than one or two."

In excerpts from a Sunday Times magazine interview, published in The Sun today, Keane added: "He's got potential, like I've got potential to be a good manager. Potential is one thing, doing it is another."

Keane is also critical of another England star, Michael Owen, for doing media work too soon after suffering an injury.

The Newcastle striker, currently recovering from a serious knee injury sustained during the World Cup, broke his foot last December and missed most of the second half of last season.

Keane said: "There's loads of people who get sucked in. Michael Owen always springs to mind. The day after Owen broke his foot, he's doing an article and I'm thinking 'Work on your recovery, man'."

The former Republic of Ireland midfielder does not spare his former United boss Sir Alex Ferguson from criticism.

Keane's interview with the club's MUTV station following a 4-1 defeat at Middlesbrough in October 2005 was pulled from transmission, and three weeks later he parted company with United after 12-and-a-half years at Old Trafford.

And Keane claims his former boss "was swayed by certain people he works with". He explained: "I was seeing players doing stuff off the pitch - had the feeling it was affecting them - and it came to a head with that defeat.

"Yes, I nailed certain people. I took the publicity with a pinch of salt, senior figures at the club should've done the same. In the end, the manager was swayed by certain people he works with."