Albert Riera’s 21st minute goal has put Watford into a 1-0 lead against Town at Vicarage Road at half-time.
Town boss Mick McCarthy made three changes from the team which beat Doncaster last week with Aaron Cresswell, Anthony Wordsworth and Frank Nouble coming into the side for Tyrone Mings, Paul Anderson and Stephen Hunt.
Anderson, who has been suffering with a hamstring problem, dropped out of the 18, as did former Watford keeper Scott Loach, who woke up with a back problem.
Hunt and Mings were on the bench, along with third-choice keeper Michael Crowe and strikers Paul Taylor and Jack Marriott, who was recalled from loan at Woking on Friday. Sylvan Ebanks-Blake missed out with a hamstring injury.
The sell-out Blues away following behind the goal spent their time throwing around a huge variety of inflatables as they waited for kick-off and were in fine voice as the game got underway.
Town, with Wordsworth in a central midfield three and ahead of him Murphy and Nouble to the left and right of Williams, started brightly, Nouble winning an early corner which came to nothing.
Murphy hit a low shot through to Watford keeper Manuel Almunia in the eighth minute after a long spell of Town passing down the left.
The Blues continued their early pressure and on 12 the home side eventually scrambled a Williams freekick from the left behind ahead of Chambers at the far post.
From the resultant corner, Wordsworth’s under-hit pass led to a Watford break which was cut out by superb Cresswell challenges on first Mathias Renegie and then Lewis McGugan.
But in the main Town were still on top and on 14 Williams forced Almunia to parry a strike from the edge of the 18-yard box, the loose ball somehow avoiding several well-placed Blues players.
However, despite Town having been on top, the home side went in front in the 21st minute. Former Liverpool man Albert Riera brought the ball inside Chambers from the left and, with no one closing him down, curled a shot beyond Dean Gerken and into the corner of the net.
The Blues immediately went looking for an equaliser, Williams tricking his way into space on the left of the area, but hitting his cross beyond his team-mates. Soon after, Wordsworth flicked a header wide from Nouble’s left-sided cross.
Town eventually cleared the increasingly influential Riera’s mis-hit shot across the face of goal in the 35th minute, then Cresswell diverted McGugan’s cross from the left wide with the Hornets looking the more dangerous side but with the Blues still having a lot of the ball, albeit largely in unthreatening areas.
On 38 Wordsworth screwed a shot wide from distance and the Blues were unable to threaten again before the break.
Having started on the font foot, the Blues had been on top until Watford’s goal. From there, the home side grew in confidence with Town looking rather lacking in ideas in the latter stages of the half.
Watford: Almunia (c), Angella, Ekstrand, Hoban, Faraoni, Abdi, Tozser, McGugan, Riera, Deeney, Ranegie. Subs: Bond, Belkalem, Battocchio, Merkel, Doyley, Murray, Pudil.
Town: Gerken, Chambers (c), Berra, Smith, Cresswell, Skuse, Hyam, Wordsworth, Williams, Nouble, Murphy. Subs: Crowe, Mings, Richardson, Hunt, Green, Taylor, Marriott. Referee: Gary Sutton (Lincolnshire).