Manchester United legend Roy Keane says the back four isn't good enough.

Keane was speaking after the derby defeat to Manchester City.

Asked about United's biggest weakness, he stated: "The back four… I don't think Shaw is up to it, Young is not a full-back. The two centre halves, take it from there. As long as you've got a decent keeper and back four, it's tough going. The foundation if you're going to win trophies… Look how many points they are behind, 25 points, It's mind-boggling.

"First and foremost, get the back five, else there's a long way back.

"I'd be shocked if they're anywhere near the top next season.

"When we were playing, if anyone had said Liverpool would go 30 years without winning the league, they'd have thought you need locking up!

"United, the years soon go by, and unless there's an improvement…

"If you invite me back next year, hopefully I'll still have a job at Forest, you'll be having the same conversation."