Jesse Lingard admitted his muted celebrations after his goal at West Ham were out of respect to the club he starred for on loan last season.
England winger Lingard reinvigorated his career with the Hammers after joining in January, scoring nine goals in 16 matches to help them qualify for the Europa League.
But there was a sense of inevitability when he came on as a late substitute for Manchester United at the London Stadium and promptly scored what turned out to be the winner.
Lingard told MUTV: "They supported me in the loan spell and gave me a great reception, so it was only right to pay them back.
"It was a great reception from the West Ham fans. I had a brilliant time here, but I had to do my bit."
Said Benrahma opened the scoring for West Ham before Cristiano Ronaldo's fourth goal in three matches hauled United level.
With two minutes to go Lingard made space for himself on the corner of the penalty area and launched a superb curler into the far corner.
It was redemption for the 28-year-old after his error cost United dearly in their Champions League defeat by Young Boys five days earlier.
"That's football. It's the highs and lows of football, and the lads and the staff and fans have been behind me all week and it was great to get minutes and come on," added Lingard.
That was not the end of the drama, with Hammers captain Mark Noble climbing off the bench to take a stoppage-time penalty, only for David De Gea to save it and secure a 2-1 win for the visitors.
Boss Ole Gunnar Solskjaer confirmed afterwards that Lingard will start against the Hammers when the teams meet again in the Carabao Cup at Old Trafford on Wednesday night.
"The main aim is to obviously win a trophy this season and I think we've got the squad depth to do that," said Lingard.
"Everyone's hungry to play and everyone's working hard in training to get in that matchday squad.
"Everyone's always ready to play, so the subs have got to be ready to make a difference.
"They're always tough games against West Ham and to play them back to back is a little bit different, but we'll go into that game full of confidence."
West Ham have now missed four of their last five penalties – although one of those was by Lingard – leaving manager David Moyes with a headache, especially if Wednesday's cup match goes the distance.
"I am concerned," he said. "We just don't necessarily have someone who is a natural penalty kick taker.
"It is an easy thing to work on because you can stand and take penalty kick in training but it's a different thing when you've got to go on the stage and do it."