Source: Team_Talk
Hornets boss signs up defender
The 20-year-old joins fellow Red Devils rookie Tom Cleverley at Vicarage Road after Mackay beat off competition from a host of clubs for his signature.
Cathcart spent last season on loan at Plymouth, making 33 appearances for the West Country club, and will link up with the Hornets after Tuesday night's trip to Home Park.
Mackay has been looking to boost his defence following Mike Williamson's deadline-day departure to Portsmouth.
