After the misfiring Romelu Lukaku was rested for the match, the Blues showed they can fire in the £100million man's absence in what was a comfortable victory at Stamford Bridge.
Lukaku had been criticised after making a record-low seven touches against Crystal Palace, but his deputies prove they have what it takes to fire in his absence, with Havertz and Pulisic putting in commendable displays in attack.
Chelsea began brightly and should have gone ahead within four minutes when Havertz flashed a shot over the bar from point blank range.
The German, who netted the winner in the Champions League final in 2021, had to do better after Cesar Azpilicueta picked him out brilliantly from out wide.
He tested Leo Jardim with a low strike moments later before Leo Jardim parried out for a corner.
And the 22-year-old finally got his goal when he headed into the net from the corner to give the Blues a deserved lead after a dominant start.
Chelsea continued to dominate the ball but Lille were soaking up the pressure well and the hosts deservedly went into half-time ahead.
Marcos Alonso fired in the best opening for Chelsea after the break in the 50th minute as his low effort was excellently kept out by Jardim.
The ball fell to the Spaniard from a tight angle after N'Golo Kante did well to squeeze a cross over from the right but he could only hit it straight at the goalkeeper.
Havertz then went on a brilliant run down the left flank before firing an effort over the bar.
Christian Pulisic doubled Chelsea's lead just after the hour mark with a delightful delicate finish over Jardim.
It came about after N'Golo Kante broke with power before unleashing the American to slot home.
Chelsea saw out the victory with ease as Lille were unable to conjure up a decent opportunity in the second-half.
They now have a commanding lead going into the second-leg and Thomas Tuchel will now be fully focussed going into the Carabao Cup final this weekend.