The Daily Star says Ferguson could also be in with a chance of hijacking Arsenal's bid for Oxlade-Chamberlain.
The Gunners are favourites to sign the teenager, who made 41 appearances for Saints last season, scoring 10 goals.
Saints manager Nigel Adkins is looking to sign at least three players with Premier League experience this summer as the club tries to emulate Norwich's achievements of successive promotions from League One to the top flight.
So he is eager to try to negotiate a player or players-plus-cash deal for Chamberlain, who turns 18 in August.
Obertan has failed to make an impact at United since his £3m move from Bordeaux in 2009.
Brown, 31, made only four league starts last season and has no future at Old Trafford.