The 24-year-old signed a five-year deal at Vicarage Road when he joined the club from Club Brugge for £3.6 million last year.
Browsing: Vicarage Road
But the Golden Boys are struggling to offload Dennis, who took to the Premier League like an eagle to the wild.
The Hornets managed to hold Manchester United to a goalless draw last time out, while Mikel Arteta’s side left it late to sink Wolverhampton Wanderers 2-1.
The Hornets went down 1-0 to West Ham United in midweek, while Graham Potter’s men have not been in action since bowing out of the FA Cup to Tottenham Hotspur last week.
The fourth new arrival of the January window for the Golden Boys, Kalu joins full-back Hassane Kamara, central defender Samir and midfielder Edo Kayembe at Vicarage Road.
The Italian, who leaves the club sitting 19th in the Premier League, managed to take just seven points from his time in charge at Vicarage Road.
Spurs will enter the contest off the back of a 1-1 draw with Southampton on Tuesday, while Watford suffered a 4-1 home defeat to West Ham United on the same afternoon.
The striker is expected to depart for the tournament after the game against Tottenham on New Year’s Day, but the head coach suggested that there may be a chance that they can keep him at Vicarage Road instead.
The hosts went down 2-1 to the Blues in midweek, while Pep Guardiola’s men saw off Aston Villa by the same scoreline.
The Red Devils suffered a 2-0 defeat to Manchester City before the international break, while Watford, who are just outside the relegation zone in England’s top flight, lost 1-0 at Arsenal in their last contest.
The Hornets, who sit 14th in the table, recorded a 5-2 win over Everton at Goodison Park last weekend, while 16th-placed Southampton played out a 2-2 draw with Burnley in their last league match.
The Hornets were sent packing 3-1 by Stoke City in midweek action, whereas Steve Bruce’s side have had over a week to recover from their 1-1 draw with Leeds United in the top flight.
Watford suffered a 1-0 loss to Tottenham Hotspur before the international break, while Wolves, who are yet to get off the mark this term, were beaten 1-0 by Manchester United at Molineux.
The Hornets’ haul of 91 points saw them achieve automatic promotion back to the big time, whereas Villa ultimately fell short in their pursuit of European football.
Just over 3,500 people were present at Vicarage Road on Saturday to see the Hornets drawing 0-0 with West Bromwich Albion as the lifting of Covid-19 restrictions permits stadiums to once again grant entry to the general public.
Buoyed by a much-needed win last time out, Watford will be looking to climb clear of the Premier League relegation zone when they host Newcastle United at lunchtime.
The Hornets currently sit just one point above the relegation zone following Thursday’s defeat at Burnley, while Southampton need just one more win to reach the 40-point mark.
The Hornets go into the match with only goal difference keeping them out of the relegation zone, whereas Leicester are flying high in third and look destined to qualify for next season’s Champions League.
Watford face Everton at Vicarage Road this afternoon in the Premier League, with the home side looking to continue their resurgence under new manager Nigel Pearson.
And soon afterwards, Sanchez Flores’ return to Vicarage Road was confirmed, three years after leaving the club.