The Blues headed into the game on the back of their disappointing 3-1 loss to Tottenham Hotspur at Stamford Bridge last weekend as they suffered a major blow to their hopes of finishing in the top four.
And Sunday’s result left them 10 points adrift of the top four in the Premier League table.
The west London side took the lead in the 36th minute at Stamford Bridge thanks to Cesar Azpilicueta’s close-range finish.
However, West Ham fought back when substitute Javier Hernandez fired home an emphatic finish in the 72nd minute.
But it was both Willian and Hazard’s displays which really impressed former defender Mills.
Speaking to BBC Radio 5 live, Mills said: “It’s a defensive nightmare [for Azpilicueta’s opener].
“A short corner again and no-one gets out to the cross, and no-one gets tight to Cesar Azpilicueta who pokes home.
“But just before that, Joe Hart made a great save with his feet, after great play from Eden Hazard and Willian again – they’ve been Chelsea’s best players today.”
After West Ham’s equaliser, Mills added: “It’s a fabulous finish from Javier Hernandez, he gets his head over the ball and fires it into the corner.”
Chelsea FC will return to Premier League action next Saturday lunchtime when they travel to St Mary’s to take on Southampton.
The west London side won the Premier League title but have struggled to produce consistent form in the top flight this term.
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