David O'Leary says Manchester United are lacking a cutting edge and need to bring in some world class players.
David Moyes' side slumped to their third consecutive defeat in all competitions with a 2-1 loss to Sunderland in the Capital One Cup semi-final first leg at the Stadium of Light, their worst run since May 2001.
Former Arsenal and Leeds defender O'Leary, who was watching the game for Sky Sports News, believes the reigning Premier League champions struggle when their front pairing of Wayne Rooney and Robin van Persie is missing.
He said: "I couldn't see Manchester United getting beat tonight but I suppose nothing should surprise you at the moment about Manchester United.
"They're lacking a real cutting edge, in particular, and they need players - in my opinion, a couple of world-class midfield players.
"If you had them and are missing Rooney and Van Persie up front then you would only be struggling a little bit.
"But it looked like they were struggling in that department tonight [Tuesday] and lacking a real cutting edge when they got around the Sunderland box."
Gus Poyet's side went 1-0 up just before half-time before Nemanja Vidic pulled one back for the visitors seven minutes into the second period.
But a controversial penalty, converted by Fabio Borini, handed Sunderland the advantage going in to the second leg at Old Trafford on January 22.
Despite having 56.1% of possession and four shots on target, United were unable to really trouble a defiant Sunderland defence and O'Leary questioned Danny Welbeck's contribution up front.
"United had a lot of good possession but they never really had that final ball," added O'Leary.
"Welbeck was up there but did he really worry Wes Brown and John O'Shea? Not particularly.
"I thought he was easy to handle out there for Sunderland and that contributed to why they won the game.
"United had all the possession but when they got it up to Welbeck he didn't look like he was going to do much with it, and [Adnan] Januzaj was the one, if any, he was going to unlock the door."
Former Red Devils striker Andy Cole, who watched game in Sunderland for Sky Sports, added: "United are playing a lot of balls in front of teams at the moment and not getting in behind.
"I think when they've got someone like Welbeck in the team who can stretch defenders with blistering pace and Januzaj - who was Manchester United's best player - they do have the quality to get in behind and cutt teams open like they used to.
"I think once they get the confidence and start stretching teams that way I think they will start winning football matches but at the moment you can see they're lacking a bit of confidence."
The victory means Sunderland claimed their first win over United since November 2000 and Cole said the club, who are bottom of the Premier League table, went in to the game with confidence - but will need to be at their best in the away leg.
"Sunderland's beat Chellsea in the Capital One Cup and their performances in the League have picked up as well, so you could sense them going in to game today saying: 'we're at home and if we can get a positive result today and beat Manchester United you never know where that can take us'.
"They were fortunate enough to win, but United are home for the second leg, at Old Trafford, so the Sunderland boys will say 'it's only half done'.
"When Man United are at Old Trafford they'll be saying to themselves 'we're still in this tie, we can win it.'"