The 22-year-old winger missed Saturday's controversial defeat at Nottingham Forest with a hamstring injury and he again remains a doubt although he will travel with the squad to Vicarage Road.
Watford's on-loan Manchester United midfielder Tom Cleverley is still suspended, so Jon Harley will hope to keep his place.Winger Will Buckley could be added to the squad following a thigh problem.
Sousa had seen Swansea denied what looked a stonewall penalty against Darren Pratley and then not been given an offside decision which would have prevented the corner from which Forest scored the winner.
Swansea midfielder Darren Pratley was left seething after not receiving a penalty in the 1-0 defeat at promotion rivals Nottingham Forest."It was embarrassing to be honest, I was five yards out from goal and my legs have been clipped," said Pratley.
Swans keeper Dorus De Vries misjudged a corner from substitute Lewis McGugan in Saturday's clash at The City Ground. The ball sailed over his head and Chambers turned the ball home from just two yards out.