Cahill has only featured for 201 minutes in all competitions this season, and the centre-back has less than a year remaining on his contract.
The 32-year-old has suggested that he may be willing to remain at Stamford Bridge until the end of the campaign in order to try to win the Europa League, but according to The Mirror, the Englishman will have offers to leave the West Londoners.
The report suggests that Southampton have identified Cahill as a potential January signing, with the Saints having struggled in defence since the start of the season.
Mark Hughes has watched his team concede a number of late goals, and it has resulted in the club sitting just above the relegation zone in the Premier League.
Southampton play host to Chelsea on Sunday afternoon.