Swansea City captain Ashley Williams says their Premier League position is a concern but that the wins will come if they keep playing the way they are.
Despite enjoying 61% possession at Old Trafford, Swansea still on Saturday.
The club's run of seven league games without a win has seen manager Michael Laudrup's side drop to 13th, just three points above the relegation places.
"We've done well and come away with nothing from the game," Williams said.
"It felt good first half, not only possession but I thought the forward players did really well - a lot of link-up play, one touch and stuff. It was nice to see.
"We knew the longer it went on the more it would benefit us. We'd done well and we weren't hanging on, we really dominated the game in the first half.
"I'm as frustrated as anyone and I'm taking as much responsibility as I can."
Antonio Valencia and Danny Welbeck struck after the break for United, as the hosts exacted revenge for the previous weekend's FA Cup defeat by the Swans - the first time the Welsh side had won at Old Trafford.
Despite that notable cup scalp, Swansea have struggled for league wins this season and Williams says they must keep their effort going to climb away from the drop zone.
"We've played well in all the games we haven't had a win and we're not coming away with the result," added the centre back.
"I just think we need to learn a few lessons quickly and just get a bit of experience in the critical moments.
"We are concerned, we've got to be concerned, but we've got to feel confident to know that what we've got in our dressing-room is enough to take us well away from that.
"There's a lot of excuses why that should be, we do have a lot of injuries.
"The difference between this season and others is we've lost our goalie [Michel Vorm], Michu our main top scorer - that's never happened - Nathan Dyer is another big player for us, Pablo Hernandez has been missing a lot.
"All of us have spent time on the sidelines, which is unusual.
"The pleasing thing is that we're all still showing confidence and the manager said that we don't look like a team that haven't won in seven [league] games.
"We've got a bit of a tough run: we knew that playing Chelsea, Manchester City, Manchester United, Tottenham it's going to be tough.
"But we need to get a win next week [against Spurs at home] and that's the focus."