The players, both born in 1994, could be loaned or sold in order to secure regular first team football away from the San Siro.
Sky Sport Italia reports that with the arrivals of Keisuke Honda and the return of Stephan El Shaarway from injury, the Rossoneri would prefer the players gain experience elsewhere before returning to Milan.
Niang could be the subject of a co-ownership swap deal between the Diavolo and Genoa, with either Juraj Kucka or Francesco Lodi moving the other way after the same move failed to materialize during the summer.
Vergara though, would likely be part of a loan deal before returning mid-way through 2014.
The Colombian, who only joined Milan this summer, was injured in early August and has yet to make an official appearance for the Rossoneri.