The French coach is keen to find a long-term replacement for Arsenal's skipper, who is hanging up his boots next summer to take up the head of academy role at the north London club.
Diallo is said to have been identified by Arsenal's new head of recruitment Sven Mislintat, who joined from Borussia Dortmund in November. The German scout believes the young French defender has the qualities to become a long-term success in the Premier League.
The 21-year-old joined Mainz from AS Monaco in the summer and is contracted to the German club until the summer of 2022. He has made 15 Bundesliga appearances since his arrival and has contributed with two goals.
The German club are struggling in the league this season and are currently in 15th place. Despite their struggles, the France Under-21 international has impressed onlookers and is currently being watched by clubs from England.
According to Goal, Arsenal are monitoring his situation at the club, but any move is said to be planned for next summer rather than the upcoming January transfer window. Apart from the Gunners, the report claims that there is another unnamed club among England's top six also keen on signing the young Frenchman.
Calum Chambers and Rob Holding are on Arsenal's books but are yet to push their way into the starting XI on a regular basis. The duo have impressed in parts, but with Mertesacker leaving, Arsene Wenger will be left with just two senior defenders in Laurent Koscielny and Shkodran Mustafi.
Mislintat looks to have been tasked to identify prospective replacements for Arsenal's skipper and has looked to his old stomping ground – the Bundesliga. According to the Daily Mail, apart from Diallo, Arsenal are also said to be looking at Wolfsburg starlet Ohis Felix Uduokhai.
The 20-year-old German youth international has made 14 league appearances for Wolfsburg, who are also struggling in the bottom half of the Bundesliga table.