The Watford Observer understands the Hornets are in discussions with Blackpool defender Craig Cathcart over a return to Vicarage Road.
Cathcart played 12 times for the Golden Boys under Malky Mackay during a loan spell in 2009 before it was ended prematurely, with the club claiming it was due to a knee injury.
The 25-year-old joined Blackpool the following summer, soon after their promotion to the Premier League, for a reported £350,000 and has remained there since, making 117 appearances during his four-year stay.
Cathcart, who has 18 Northern Ireland caps, is out of contract this summer and remains in ongoing talks with the Hornets ahead of a move.
If the former Manchester United defender has a medical with the club, it will show he has an enlarged heart which has to be monitored regularly and resulted in him missing the first leg of Blackpool's Championship play-off semi-final first leg in 2012 as a precaution.
Cathcart is a centre half who is comfortable on the ball and can also play at right back.
Watford have already signed one centre half this summer in former West Bromwich Albion and Doncaster Rovers centre back Gabriel Tamas.