'Meddling my fault' - Ferguson
Sir Alex Ferguson admitted his tactics backfired as Manchester United were forced to come from behind to avoid an FA Cup exit at Southampton.
The League One side bossed the first half and deservedly broke the deadlock on the stroke of half-time, with Richard Chaplow smashing Saints ahead.
However, Ferguson's introduction of Nani and Ryan Giggs 13 minutes into the second half gave United the impetus and width that had been severely lacking.
First Michael Owen levelled with his first goal since September, before Javier Hernandez ghosted in to wrap up the fourth-round tie with a quarter of an hour remaining.
While the history books will show a United victory, Ferguson admits his decisions left the side on the back foot from the offset.
"Sometimes we make it difficult for ourselves but, in fairness, I maybe meddled with the system somewhat this afternoon," he told MUTV.
"We tried a diamond in the middle of the pitch and, of course, Manchester United are used to playing with width all the time and I think that was a problem for us.
"It wasn't working at all," he added.
"We had some possession of the ball but we never really threatened. We had two or three shots from the edge of the box.
"It was a nothing first half, really, and the goal, if anything, made us play.
"(Southampton) scoring the goal right on half-time motivated us a bit to do better."
Ferguson admitted the timing of Owen's goal was important to ensure the game did not get away from them, while he praised Hernandez for his clinical finishing, saying: "He only had one chance today: one chance, one goal."
The United boss also revealed that United should have their first-choice back four for the clash with Aston Villa on Tuesday, with Rafael, Nemanja Vidic and Rio Ferdinand likely to return.
Southampton manager Nigel Adkins, meanwhile, expects precocious winger Alex Oxlade-Chamberlain to remain at St Mary's for the rest of the season.
Speculation over the 17-year-old's future has been rife throughout January, with Arsenal and Liverpool mooted as a potential destination.
However, Adkins insists that Southampton have no intention of selling him despite interest from some of the Barclays Premier League elite.
"We are not envisaging selling him, we're not looking to sell him," he said after the match. "We don't want to sell him.
"I think it is beneficial for him to be playing regularly for Southampton in the Football League, giving him a chance to develop.
"Yes, he is well courted and you can see today that he has ability about him. Southampton Football Club are not looking to sell Alex Chamberlain."
Adkins admitted he would not be surprised if Ferguson enquired about Oxlade-Chamberlain when they spoke later on, but the Saints boss insists the clash with Exeter remains his primary focus.
"There is always going to be mass speculation; there has been throughout the transfer window," he said.
"It shuts at 11 o'clock on Monday evening and there will be mass speculation all the way up until then.
"All we can do is control the controllables, which is getting Alex ready with the group in preparation for a very big game for this football club on Tuesday night at Exeter."
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