Sinclair suffered a slight hamstring niggle, while Dobbie also turned his ankle in a freak training ground accident ahead of Saturday`s 3-1 defeat at Nottingham Forest.
But both are set to return for the clash at Vicarage Road as the Swans look to record their first points of the season on the road, with all 12 to date coming at the Liberty Stadium.
David Cotterill limped off at half-time at the City Ground nursing a minor groin problem but midfielder Darren Pratley completed the game despite sustaining a painful shoulder injury.
Both will be assessed over the next 24 hours but should be okay.
Manager Rodgers will be keen to end Swansea`s away woes at Watford, although he cannot be guaranteed a warm reception by the club he walked away from last June - after little more than six months in charge - to take over at Reading.