Defender Craig Cathcart has signed a new four-year deal at Watford.
The 26-year-old Northern Ireland international made 30 appearances for the Hornets last season as they won promotion to the Barclays Premier League.
Cathcart, who started his career at Manchester United, signed for Watford from Blackpool last summer.
Watford, under new head coach Quique Sanchez Flores, have already been busy during the close-season, with Matej Vydra turning his loan move from Italian side Udinese into a permanent deal and Gabriele Angella penning a new five-year deal on Wednesday.
Newly promoted Watford have signed Austrian international defender Sebastian Prodl on a five year contract from Werder Bremen.
The 27 year-old has represented his country 44 times and had also been attracting interest from Leicester.
A Watford football fan has received "life-threatening injuries" after being attacked in the street following a match, West Midlands Police said.
The 44-year-old was on his way home with friends from Wolves' ground at Molineux to Wolverhampton train station when he was assaulted and suffered a serious head injury.
Detective Sergeant Adam Keen said: "The group of friends were completely outnumbered and the victim suffered a severe head injury which has left him in a critical condition in hospital.
"His family have been informed and we are in the process of taking statements from witnesses and locating any CCTV which might have captured those responsible for the attack.
"I would urge anyone with information which will help our investigation to contact me as soon as possible on 101."
Watford FC issued a statement about the incident which said: "The thoughts of everyone associated with Watford FC are with a Hornets' supporter - at yesterday's game - who is now critically ill after an unprovoked post-match attack."
Watford have announced their fourth manager in six weeks, appointing Slavisa Jokanovic as boss.
The former Chelsea midfielder replaces Billy McKinlay as head coach, after the Scot managed just eight days in charge.
Speaking about the arrival of Jokanovic, owner Gino Pizzo said: "Our job is always to act in the best long-term interests of this football club. There can be no compromise on this - whatever the circumstances.
"I fully support and endorse the view from our technical staff that, given the talented squad which has been assembled and our position in the league, an experienced head coach with a winning pedigree is of primary importance to help ensure the success we are all striving for."
Watford will be searching for their fourth manager in just over a month, as Billy McKinlay is set to depart Vicarage Road after just two games in charge.
The former Scotland midfielder replaced Oscar Garcia as head coach after the Spaniard was forced to quit due to health reasons, picking up four points from the six available.
Garcia only arrived in September following the resignation of Giuseppe Sannino.
After eight days at the helm it looks certain the Watford boss will leave the Championship's third-placed club, but it remains unclear whether he has resigned or been sacked.
Watford goalkeeper Jonathan Bond has been taken to hospital after colliding with Leed's United player Dominic Poleon during their 2-1 defeat:
Watford FC striker Troy Deeney has been jailed for 10 months for taking part in a savage attack on a group of students outside a nightclub.
The 23-year-old was caught on CCTV as he kicked one of the victims in the head during a night out, Birmingham Crown Court heard.
Deeney, who pleaded guilty to affray at an earlier hearing, was arrested shortly after the fracas, which left one man with a broken jaw and another requiring 20 stitches to a mouth wound.