The Blues suffered a surprise 1-0 loss to Leicester City at Stamford Bridge on Saturday to finish on a sour note before Christmas Day.
Chelsea FC are in fourth place in the Premier League table but Maurizio Sarri’s side are coming under pressure from Arsenal.
The Gunners are level on points with their London rivals but Chelsea FC hold the advantage thanks to their superior goal difference.
Chelsea FC will make the awkward trip to Watford on Boxing Day as the Blues look to beat a Hornets team that has won their last two games.
Watford eased to a 3-2 win over Cardiff City but a 2-0 victory at West Ham United to sign off on a positive note ahead of Christmas Day.
Former Arsenal midfielder Merson believes Chelsea FC will secure a narrow 2-1 win against Watford at Vicarage Road on Boxing Day.
“The defeat by Leicester was a shocking result for Chelsea,” Merson told Sky Sports.
“I was at the game when they drew with Everton and before that match, they were title contenders. Now they are fighting for the top four. That loss has also now opened the door to Man Utd, believe it or not.
“Watford will be a hard game, they are physical and decent and they had an unbelievable result the other day winning at West Ham, it was a great win.
“But you just do not know what you are going to get with Watford – one minute they are brave and fit, the next they are getting beat 4-0 at home by Bournemouth. But I am just going to go with Chelsea here…”
Chelsea FC finished in fifth place in the Premier League table last term to miss out on a spot in the Champions League.
The Blues look to be facing a straight shootout with Arsenal to secure fourth spot in the current campaign.
Both Arsenal and Chelsea FC underwent a change of management in the summer following the arrivals of Emery and Sarri.
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