Ronald Koeman praised Charlie Austin's "amazing" debut after Southampton's new striker scored the winner at Old Trafford.
Saints got an immediate return on their £4m outlay as the signing from QPR headed his new side to a second successive 1-0 win at Manchester United.
And, according to Koeman, Austin's late goal meant a gameplan executed to perfection after United had just one shot on target.
"That's why we signed the player," the Saints boss said of his match-winner. "Of course it's an amazing feeling for him and for the team that he scored the winner. He did a great job like everybody in the team.
"We had very good organisation on the pitch, we made it very difficult for United and had good pressing from the three players in front.
"Maybe it was not at that level offensive-wise because in the first half we had to create more chances than we did, but the whole team performance was good enough to win today."
Louis van Gaal switched to three centre-halves to counter the threat of Shane Long, Sadio Mane and Dusan Tadic, a move Koeman called "a very big compliment".
And he is looking for his side to improve their position - currently eighth - now that three straight victories have banished the memory of winning just one of their previous eight in the league.
He said: "We like to fight. We have our own ambition to go up the table and it's all about winning games. We have a third win in a row but we know every week it's difficult."