Olivier Giroud's first-half double set up a comfortable 4-0 home win over 10-man PAOK in which Callum Hudson-Odoi opened his Chelsea account, Maurizio Sarri's side topping Group L after extending their run of wins to five matches.
BATE's 2-0 home defeat of Vidi earlier in the day ensured Chelsea could not be caught in top spot, with Sarri making 10 changes from a crushing 3-1 loss at Tottenham that ended their unbeaten start to the Premier League season last time out.
Yevhen Khacheridi's early red card gave Chelsea's young guns plenty of chances to fire but it was Giroud's well-taken brace before the break that put the Blues on track for victory.
And 18-year-old Hudson-Odoi hit his first Chelsea goal with a fine finish before substitute Alvaro Morata headed a late fourth, with Group L's bottom side PAOK now unable to qualify.
Khacheridi's dismissal in the seventh minute left PAOK in deep trouble, the centre-back tripping Giroud as the France striker ran on to a loose pass from Leo Matos.
Hudson-Odoi was proving lively and another Chelsea youngster, Ruben Loftus-Cheek, forced a superb fingertip save from Alexandros Paschalakis with a fizzing 25-yard drive.
Chelsea's opener arrived in the 27th minute, a long ball over the top from Cesc Fabregas beautifully controlled by Pedro, who held the ball up to wait for support and laid it off for Giroud to pass a first-time finish across Alexandros Paschalakis.
Hudson-Odoi, making his first Europa League start, then hit the crossbar with a 20-yard curler but Giroud's controlled volley from another lovely lofted Fabregas pass doubled Chelsea's advantage and recorded his fourth goal in three games for club and country.
Teenager Hudson-Odoi scored the goal his vivacious performance deserved on the hour-mark, cutting in off the left flank to rifle a right-footed drive inside Paschalakis' near post, with Fabregas collecting another assist.
Andreas Christensen's substitution due to injury was a sour note for Chelsea, who were able to rest Giroud and Pedro in the closing stages with Group L's top spot in the bag.
And with 12 minutes to go Giroud's replacement Morata nodded in Hudson-Odoi's right-wing cross to complete the scoring.
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