Now in his second spell as interim manager of Chelsea veteran Dutch boss Guus Hiddink has steadied the ship at Stamford Bridge and is yet to lose in eight games at the helm.

His first was the 2-2 draw with Quique Sanchez Flores’ side on Boxing Day where a missed penalty from Oscar saw the Blues pass up the chance to hand their new boss a first win.

Hiddink, who has previously managed PSV Eindhoven (twice), Valencia and Real Madrid among numerous others, was Chelsea boss on a caretaker basis in 2009 following the sacking of Luiz Felipe Scolari.

The former Netherlands manager won the FA Cup and proved hugely popular at Stamford Bridge to the point owner Roman Abramovich tried to persuade him to remain beyond the end of his original agreement.

However, a man of his word, Hiddink turned down the opportunity to stay and took on the role of Turkey coach as previously agreed.

He lasted just a year at the helm before similarly brief spells with Anzhi Makhachkala and the Netherlands preceded his return to the Premier League.

This time he replaced Jose Mourinho who was sacked, despite the outcry of Chelsea fans, on December 17 with the defending champions floundering just above the relegation zone.

Here we profile three players who could make the difference against the Hornets tonight.

Watford Observer:

Diego Costa: The tempestuous forward looks to have returned to something like his best form since Hiddink replaced Mourinho in the Chelsea dugout, scoring six in his last eight.

Two goals against the Hornets in the 2-2 Boxing Day draw at Stamford Bridge kick-started that run for the Spanish international who had previously registered just four in 20 appearances for Chelsea.

Signed from Atletico Madrid in 2014 after scoring to help knock the Blues out of the Champions League at Stamford Bridge, the 27-year-old netted 35 times in 41 outings for Atleti in his final season in Spain.

That form prompted Mourinho to spend £32 million bringing him to the Premier League, money which was more than justified as he grabbed 20 goals during his first season at the club en-route to winning the league and League Cup.

Watford Observer:

John Terry: The former England international looks set to depart Stamford Bridge at the end of the season after 21 years with the west London club.

The news broke on Monday evening with the 35-year-old centre-back – the last player to break through the club’s Academy setup – revealing he wouldn’t be offered a new deal for next season.

Terry has played more than 600 times for the Blues and won 16 major honours during his including four Premier League titles, five FA Cups, the Champions League and the Europa League.

He was controversially hauled off at half-time of Chelsea’s 3-0 defeat at Manchester City on the third weekend of the season and it was suggested by hysterical Sky Sports pundit Niall Quinn that would be the end of his Blues career.

The former Nottingham Forest loanee has made a habit of proving people wrong and, much like he did when Rafa Benitez claimed he couldn’t play twice a week, he has battled to regain his place.

Watford Observer:

Thibaut Courtois: The imposing Belgian has seamlessly replaced the ever-popular Petr Cech as Chelsea’s number one and is in his second season as first-choice between the sticks.

Brought to Stamford Bridge from Genk in 2011, the 6ft6in keeper spent the next three seasons on loan at Atletico, making more than 100 appearances for the Rojiblancos before being brought back to England to succeed Cech in 2014.

A full Belgium international, Courtois won La Liga, the Copa del Rey and Europa League during his loan stay at the Vicente Calderon as well as finishing as a runner-up in the 2014 Champions League final as rivals Real Madrid prevailed in extra-time to seal La Decima.

At 23 the giant keeper looks set to follow in the footsteps of Cech, who last summer joined Arsenal after a season of serving as the Belgian’s deputy, and become the Blues’ number one for many years to come.