The Hammers summer signing started at left-back as his side lost 2-1 to Chelsea in Monday's opener.
With Aaron Cresswell out for around four months, Masuaku is likely to be Slaven Bilic's first-choice left-back for the foreseeable future, and Hammers fans got their first look at the new signing in action on Monday night.
The former Olympiacos man suffered disappointment on his English bow as Diego Costa's late strike won all three points for the home side at Stamford Bridge.
The 22-year full-back admitted to the West Ham website after the match that he was taken aback by the pace and physical nature of the Premier League, and suggested that he is not yet 100 per cent up to speed.
Masuaku said: "All the players were disappointed because we conceded the goal in the last minute. I thought was the game was in our hands but unfortunately we let in the second goal. We just have to keep working hard together as a team.
"I really enjoyed my Premier League debut as it was always my target to play in England since I was a youngster.
"The Premier League is very fast and for me it was tough physically as I am not 100 per cent yet. I just want to keep going, work hard and hopefully show my best form."
Hammers supporters and Bilic will be hoping that Masuaku adjusts quickly, as the games continue to come thick and fast.
Next up is a Europa League play-off meeting with last season's conquerors Astra Giurgiu, a game which Masuaku may feel more confident heading into as he boasts 16 Champions League and Europa League appearances from his time at Olympiacos.