It was the third time in four games that Sesko has scored after coming off the bench and secured points for United.
"I believe in me and so do the other players as well," Sesko told Sky Sports. "They know what they are going to get when I arrive in the game. It's up to me to deliver of course."
His goal with 19 minutes remaining finished off the slickest move of an otherwise stodgy game on Monday night.
Bryan Mbeumo controlled Matheus Cunha's superb long ball and played a perfectly weighted pass to the feet of Sesko, who steered the ball past Jordan Pickford with aplomb.
"It was a great finish," United interim coach Michael Carrick said. "It was a ruthless finish. I liked the way he put it away with real confidence. It was great play from Cunha and Mbeumo to set it up and we are dangerous on the break."
Until then defences had been on top and the lack of attacking fluency was not helped by a heavy pitch that appeared to slow down both teams.
The result took fourth-placed United three points clear of Chelsea and Liverpool. United are three behind Aston Villa.
It also extended Carrick's unbeaten run to six games since he replaced Ruben Amorim on January 13.
The defeat was a blow to Everton's hopes of a place in next year's European competitions and left it languishing in ninth, behind Brentford and Bournemouth and eight points adrift of Chelsea and Liverpool.
David Moyes' men have gone seven games without a win at their new Hill Dickinson Stadium.
"Generally we did very well in lots of bits," Moyes said. "We got done on the counterattack and they ran away and got the goal that was there. We put in a great effort to get the goal but lacked the quality to make it count."
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