The west London club will be looking to find some consistency heading into the final 15 games of the season as they look to climb the Premier League table.
Chelsea booked their place in the fifth round of the FA Cup on Sunday afternoon thanks to an impressive 5-1 win over MK Dons.
The Blues were in impressive form as they ground out a 1-0 win at Arsenal in the Premier League in their most recent top-flight outing.
And former Arsenal man Merson is tipping the west London side to claim all three points when they head to Vicarage Road on Wednesday evening.
Merson told Sky Sports: “Chelsea should win this one. They’ve got the players to do just that and they seem up for it now.
“The players may be the same but Chelsea are a different team to when Jose Mourinho was there. Since Guus Hiddink has come in the players have really upped their games.
“Cesc Fabregas looks like the player he used to be, as does Diego Costa. If Chelsea can keep Troy Deeney and Odion Ighalo quiet they win this game. It’s quite simple. I see a 2-1 Chelsea win with Costa scoring first.”
Chelsea are currently in 13th place in the Premier League table.
The Blues will host Manchester City in the fifth round of the FA Cup later this month.
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