Sir Alex Ferguson feels the introduction of Paul Scholes and Javier Hernandez was key to Manchester United's 3-2 win over Southampton.
Ferguson was able to mark his 1,000th league game in charge of United with a victory thanks to Robin van Persie's dramatic stoppage-time winner that completed the Dutchman's hat-trick.
Van Persie had earlier missed a penalty as the game appeared to be slipping away from the Red Devils at 2-1 down with just minutes remaining.
After cancelling out Rickie Lambert's opener, Morgan Schneiderlin had put Saints ahead again and it took the introduction of Scholes, Nani and Hernandez to turn the game late on.
"Van Persie scored a fantastic equaliser for us (to make it 1-1 before the break) and second half you think let's just get down to business and get this done," Ferguson told Sky Sports.
"But credit to Southampton they kept loading the ball into the box.
"Everything we did in preparation for the game has all been to deal with back-post crosses and they scored two goals off them so that was disappointing.
"But credit to Southampton they are good at it.
"For that period we were well out of it until Paul Scholes came on the park.
"His vision and consistency of passing gave us complete control of the game.
"Then it was just a matter of getting the goals of course and Van Persie has come up with them.
"He's got four goals in two starts and he'll get better.
"I think Chicharito made a difference too. He started stretching them and making fantastic runs off the ball. I was delighted with his performance."
United again looked shaky at the back despite the fact that Ferguson was able to pair Nemanja Vidic and Rio Ferdinand together at centre-back for the first time in this calendar year.
But Ferguson believes his team will improve defensively once he can get some stability in his back four.
"When you play two centre-backs together regularly you get results," added Ferguson.
"It's always been the case - with (Steve) Bruce and (Gary) Pallister, (Jaap) Stam and (Ronny) Johnsen and last season with Evans and Ferdinand playing regularly.
"This season we've had four centre-backs injured for the first game. Carrick has played centre-back at Everton and we've had Valencia at right-back.
"With the best will in the world you know that's never going to be a perfect solution.
"If we get the centre-backs back that'll give us a really good chance."