The defending Premier League champions have struggled to defend their top-flight crown in the 2017-18 season under Antonio Conte.
The Italian head coach led Chelsea FC to title glory last season after the Blues finished seven points ahead of runners up Tottenham Hotspur.
However, the west London side have lost four of their last six Premier League games to leave Chelsea FC five points adrift of fourth-placed Spurs.
Willian has been Chelsea FC’s outstanding performers in recent weeks following goals against FC Barcelona and Manchester United.
Hazard remains a threat but the Belgium international has struggled in a lone striker role in Chelsea FC’s biggest games.
Former Arsenal star Merson believes Hazard and Willian will help to fire Chelsea FC to victory over Tottenham at Stamford Bridge on Sunday evening.
“I know Chelsea’s record hasn’t been great lately, they’ve won five of their last 18, but I still fancy them to win this football game with the way Willian and Eden Hazard are playing too, especially Willian,” Merson told Sky Sports.
“Tottenham are not the greatest team away from home for where they are in the league so for me, I think the top-four race will be blown wide open.”
Chelsea FC were 2-1 winners against Tottenham at Wembley in the Premier League back in August thanks to Marcos Alonso’s two goals.
The Blues signed Everton midfielder Ross Barkley, AS Roma defender Emerson Palmieri and Arsenal striker Olivier Giroud in the January transfer window.
The west London side will take on Southampton in the FA Cup semi-finals.
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