Wanderers earned their first ever Premier League victory at Old Trafford thanks to a second-half strike from Joao Moutinho and they were good value for the win, with David de Gea making a string of saves early on to keep the scores level.
Speaking after the game, United boss Rangnick admitted his side had been well off the pace.
“We didn’t play well at all. Neither individually, nor collectively. In the first half we had big problems to keep them away from our box and from our goal,” he told Sky Sports.
“In the second half we changed to a different formation with a back three and we had more control. We then had a 15-minute spell when we could have scored; hit the crossbar.
“The goal we conceded, we had enough players in the box but we allowed [Adama] Traore with his back to goal to turn and gain speed and bring in a cross.
“The cross had already been defended by Phil Jones but again the goal we conceded was one of too many this season where Moutinho could just shoot completely unmarked with no problems, no pressure at all.
“Therefore we are very disappointed about the result but also parts of the performance.”
At the break Rangnick decided to switch his side to a back three in an attempt to get a firmer grip on proceedings.
“They were playing with almost four or five central midfielders and we were struggling to control that part of the pitch. Whenever they tried to release via their wing-backs we were also struggling,” he explained.
“That’s why we decided to change our formation and we had more control in the second half.
“But we missed our chances to score and again we have to admit that they deserved to win.”
Rangnick continued: “We didn’t press at all. I mean we tried to in the first 10 or 15 minutes but we were not able to get into those pressing situations because as I said, they had an overload in the centre of midfield.
“This is the big issue. We have only been working for two-and-a-half, three weeks because we had to close Carrington. We have had the results and at times we played well but today we have to admit they were better than us.”