The Red Devils winger has only scored two goals in the Premier League so far this season after he moved to Old Trafford from Eredivise side PSV Eindhoven in the summer transfer window.
When playing in the Premier League, you have to be on top of your game every time
Memphis has only just won his place back in the United side after the 21-year-old capitalised on Wayne Rooney’s recent absence through injury to start the Red Devils’s last three league games.
The Red Devils midfielder explained that he wasn’t expecting Premier League defences to be so strong and fearless ahead of United’s trip to Stoke City on Boxing Day.
“It’s frustrating. I know I can do a lot better,” Memphis told Sky Sports.
“I just had to settle in and get used to the football, to my new life in England. Failure just isn’t an option.
“When playing in the Premier League, you have to be on top of your game every time. The difference is enormous.
“Defenders are physically strong, very fit and aren’t afraid of anything. That was new to me. Good just isn’t enough when you’re playing for United.”
Memphis was United’s first signing of a busy summer of transfer activity at the 20-time English champions.
The 21-year-old Red Devils winger has scored three times in 21 appearances in all competitions for United so far this season.
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