The Saints have lost five first-team stars already this summer as Luke Shaw, Adam Lallana, Rickie Lambert, Dejan Lovren and Calum Chambers have all left the club, with Morgan Schneiderlin also tipped to be heading for the exit door.
New manager Ronald Koeman has already added Dusan Tadic, Graziano Pelle and Ryan Bertrand but will need more signings to keep Southampton competitive in the Premier League this season.
Hernandez has been linked with a move away from Old Trafford for some time after failing to establish himself as a regular in the starting lineup and Southampton will hope that the guarantee of first-team football can convince the Mexican striker to make the move to the south coast.
The Saints will also try to sign a Manchester United winger with Zaha and Young both targets, though they will wait to see which of the pair Louis van Gaal is prepared to sell.
Ashley Young has been impressing at left wing-back on the Red Devil's US Tour during pre-season and is unlikely to be allowed to leave, though Zaha could be available after Van Gaal revealed that it will be difficult to fit the Englishman in his first-team.
The Saints will hope that they can complete a double swoop for Hernandez and either Zaha or Young as they prepare for the new season with what will very much be a new-look Southampton side.
The club are expected to spend up to £70million this month to ensure that they remain a force in the top flight during the new season, and moves for Hernandez, Zaha and Young certainly show ambition.