The 22-year-old is unsettled in Hertfordshire for a number of reasons, according to Sky Sports News HQ, but most notable is the impending departure of Walter Mazzarri, the Italian manager who brought him to the Premier League.
Niang was identified as a player with plenty of potential when he was plucked from Caen by the Rossoneri in 2012. His natural athleticism hasn't waned, but the forward is blighted by poor decision-making and confidence issues, as evidenced by his spot-kick woes in December.
In England, the Frenchman has turned out 15 times for the Hornets, only troubling the scoresheet on two occasions. He headed straight down the tunnel after being substituted 71 minutes into last Monday's 4-3 loss to Chelsea.
Watford ends its 2016-17 term with a visit from Manchester City on Sunday.