The Italian worked with the Pozzo family while at Udinese and says they still enjoy a good relationship.
Despite guiding the Hornets to safety on their return to the Premier League, and taking them to an FA Cup final, current Watford boss Quique Sanchez Flores has been widely tipped to leave the club this summer.
A slump in form during the second half of the season has only increased the pressure, with Watford recording just two wins in 11 games.
The club insists it will decide on the manager's future at the end of the season, but the Daily Mail this week claimed that Guidolin, who worked under the Pozzo family at Udinese, could be in line to take over,
When asked about his time there, PA Sport quoted Guidolin as saying: "We worked very well together. In five years we were four times in the European positions, two in the Champions League playoff and two in the Europa League.
"But I don't know what happens at Watford."
Those comments are unlikely to dampen speculation linking Guidolin with the job at Vicarage Road, particularly with the 60-year-old's future at Swansea looking increasingly uncertain amid speculation that former boss Brendan Rodgers could be lined up for a stunning return to the Liberty Stadium.
But Guidolin insists he is focused on the job at hand in South Wales, urging his players to officially preserve their Premier League status with a result against Liverpool this weekend.
"Every week I speak to my players and, at the moment, mathematically it is not sure," he said.
"We need points. After that we can speak about other situations and other problems, but all I want is to make sure we are safe mathematically."