He made a promising start at Old Trafford, making 13 appearances in a row but he suffered a dip in form. Memphis made his first league appearance on Saturday after being substituted at halftime during the 3-0 loss to Arsenal on Oct. 4.
The 21-year-old, who was named in the starting line-up largely due to injuries to key strikers Anthony Martial and Wayne Rooney, made the most of the chance and scored after just 11 minutes, volleying home an Ander Herrera cross.
"I think every young player goes through things but I keep training and enjoy the training sessions," Memphis told the club's website (www.manutd.com).
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"The stuff (I am learning) has stuck with me and Ryan Giggs has given me good advice and I've been working on some things with him.
"You need that backing and you need to back yourself and train well, and of course all the help is great to get through difficult times.
"I like to score goals. It was important for me to score a goal when I got a chance. I was happy."
The win saw United briefly go on top of the table but were leapfroggged by Leicester City by the end of the day.
Youngster Jesse Lingard said the last-gasp win over Watford signalled a statement of intent to the other title contenders.
"It's a bit of a statement to the other teams, who will look at this and see we've won. It puts a bit more pressure on them, but it's a good feeling to be back up there," Lingard said.
"There are a lot of games coming up, we've got a lot of injuries at the moment and have to adapt to that, I thought we did that well today. As long as we win as many games as we can over Christmas, I think we'll be fine."
United will be looking to seal their progress to the next round of the Champions League when they take on PSV at home on Wednesday.
(Reporting by Shravanth Vijayakumar in Bengaluru; editing by Sudipto Ganguly)
