But the belief of Everton's recruitment team, built up over a year of monitoring him and 'several' trips to France to watch him in the flesh, is that he has the physical attributes to thrive in the Premier League.
People who know Nkounkou talk up his pace and power - "the profile of a modern left-back" they say - who is also strong in one-v-one defensive situations.
At Marseille, comparisons with their former left-back Taye Taiwo were made, while the people around Nkounkou believe he has a similar profile and attributes to Manchester City's Benjamin Mendy and Ferland Mendy, of Real Madrid.
His favourite player in his position in Real's Brazilian left-back Marcelo.
Unsworth, having seen the player up close for the first time this week, has talked of a "great athlete" but where Nkounkou will develop, first with the u-23s and then Ancelotti, is from a tactical point of view and learning how to play the position at the top level.
Everton were also hoping he would learn from both
Lucas Digne and
Leighton Baines, over the course of the next 12 months, but the latter's retirement has left the Blues now scouring the market for a replacement.
The plan is, Nkounkou will spend most of the season playing for Everton's second string but the expectation is that he will train with Ancelotti's squad as soon as possible, with the senior players due back later this month.
Hope is that he will "progress fast".
Ancelotti's influence on helping Everton beat off competition from Juventus and RB Leipzig has been well documented but Nkounkou had been on the club's radar while Marco Silva was still in charge.
