Captain Nemanja Vidic has criticised Manchester United for their defending in their last two games.
United beat Southampton 3-2 on Sunday, after defeating Fulham by the same scoreline eight days earlier, and are still without a clean sheet this season.
Goalkeeper David de Gea paid the price for a mistake against the Cottagers by losing his place for the trip to St Mary's while a much-changed defence featured two midfielders, Antonio Valencia and Michael Carrick, during the 1-0 loss at Everton.
Until Robin van Persie rescued United with a hat-trick on the south coast, they were threatened with a second defeat in three games but, despite the eventual result, Vidic was not happy.
"It was a difficult game and we conceded two goals we're not happy with at all," he told MUTV. "We've been told before the game what Southampton's strengths are, what their game is and what they're trying to achieve. In the end, they did it so it's disappointing."
Vidic was paired with a fit-again Rio Ferdinand for the first time since December although the Southampton goals were attributable to the full-backs, with Rafael da Silva beaten by Rickie Lambert for Saints' opener and Morgan Schneiderlin getting the better of Patrice Evra for the second.
"I think it's only the second time in a year myself and Rio have played together so it's a long time and obviously it's tough as everyone needs more games," Vidic added.
"I have to say, we are not really pleased with the goals we've conceded. There was a lack of concentration, I think, for all four goals we lost [in the last two games] but we have to work on it. You have to say we've had a lot of turbulence in defence with so many changes and people going in and going out.
"We didn't have a constant back four and sometimes it causes a problem, but we look forward to the next games. We have over a week to improve our fitness and obviously our form so we are going to be right for the next game in the Premier League."