Some had written the 21-year-old off after nervy showings for the Hammers in pre-season.
But Diop has firmly established himself as one of the first names on the teamsheet and is on his way to becoming a West Ham star.
The former Toulouse man's performance in a 3-1 win over Manchester United drew praise from Jose Mourinho who described Diop as a 'monster' and praised those behind West Ham's recruitment for signing him.
Diop has forged a solid partnership with the more experienced Fabian Balbuena as he seemingly gets better with every game.
But the 6ft 4in centre back, who has set his sights on a senior France call-up, is not resting on his laurels.
Speaking to West Ham's official website Diop explained what the key differences are between life in Ligue 1 - where faced the likes of Kylian Mbappe, Neymar and Edison Cavani - and the much-vanuted Premier League.
“(The Premier League) is a championship where you have to be very, very strong in transition,” Diop told whufc.com.
"For me it's the biggest difference from France. Offensive players are all talented and very athletic, more than in France.
"There are not necessarily more physical battles but the players are faster and more beefy.”
The defender praised his West Ham teammates for helping him settle into life in East London.
And he is fiercely focused on one day realising a dream of representing world champions Les Bleus.
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