Cape Town - Manchester United manager Louis Van Gaal conceded that his decision to throw winger Adnan Januzaj on for defender Cameron Borthwick-Jackson played a part in Saturday's 1-0 home Premier League defeat by Southampton.
An inviting cross from the right flank presented Charlie Austin with a dream debut for the visitors and he powered home an unstoppable header three minutes from time.
"I wanted to win this game and that's why I changed Borthwick-Jackson for Januzaj," said Van Gaal, whose side enjoyed a smash-and-grab 1-0 win at Liverpool last week despite a similarly listless display.
"That is the risk you take, it was a poor game and we didn't create so much and neither did our opponents."
"I had a feeling they could only score from set-play."
A resolute Southampton repeated their success in the corresponding fixture last season when a Dusan Tadic goal gave them their first league victory at Old Trafford in 27 years.
With their midfield stifled, United lacked any spark or creativity and their afternoon was summed up by several harmless efforts from lone striker Wayne Rooney.
A mouse appearing on the pitch in the second half drew one of the loudest cheers from a subdued home crowd, who jeered Van Gaal down the tunnel.
The Dutchman acknowledged United were feeling the heat again after the defeat ended a mini-revival following a very poor run in December.
"Because you have to meet expectations and the expectations are very high, that gives a lot of pressure for the players," he said.
"They (the fans) are right, I cannot deny that. We are working hard but we have a lot of injuries that you cannot change.
"In better or for worse, we have to stick together."
Southampton manager Ronald Koeman was delighted by his team's performance.
"We played very good," he said. "Our organisation was good, we were very compact, we had good pressing.
"We stayed in the game, controlled the game and you saw more nerves in the Man United team and finally we score from a corner kick.
"We showed spirit today, it was an amazing result for the second time here."