The Spaniard watched on as his charges sealed a comfortable victory over United and former Everton boss David Moyes at Goodison Park.
A Leighton Baines penalty and a clinical Kevin Mirallas finish in the first half secured victory, which keeps Everton a point behind Arsenal in the race for fourth spot with three matches remaining.
Though Martinez's men often dominate the ball, they had just 39 per cent of possession against last season's champions.
However, Everton were far more dangerous than their opponents, opting to utilise the pace of Romelu Lukaku and Mirallas to hit United on the counter-attack.
"You work on being adaptable, with where you are in the game and what the situation is," Martinez told Sky Sports.
"It's very pleasing when you've got young players in their early 20s who can cope with those aspects of the game so well.
"We had to be solid, very well organised and the use the dynamic football that we have.
"The way we got into the final third was very enjoyable and then we worked very hard to keep a clean sheet. The manner in which we did that was very pleasing."
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