The Blues were huge favourites heading into this match, but despite having 72% possession in the first period, they only managed to produce two efforts on target, and went into the break frustrated with the scoreline at 0-0.
Enzo Maresca brought on Levi Colwill and Noni Madueke at half time, and the visitors ran out with a renewed intensity in the second period that was quickly rewarded with a 49th-minute opener when Tyrique George pounced to score his first senior goal for the club.
What followed was a second half in which Goncalo Feio's Wojskowi were thoroughly dominated, and Madueke doubled his side's lead with more than half an hour to play, courtesy of some fine work by Jadon Sancho.
Christopher Nkunku had the chance to make it 3-0 from 12 yards, but the low-on-confidence forward saw his penalty saved by goalkeeper Kacper Tobiasz, though Madueke was on hand to put the ball in the back of the net only 25 seconds later.
After coming out a defensive state, the hosts almost pulled one back in the dying moments through winger Patryk Kun, but Chelsea's Filip Jorgensen made sure that he left the stadium with a clean sheet.
SPORTS MOLE'S VERDICT
Legia Warsaw were undoubtedly underdogs coming up against the favourites to win the Conference League, and the tie may be over before a ball has even been kicked in the second leg after they lost 3-0 on Thursday.
To make matters worse, the Wojskowi have now won just three of their last eight matches across all competitions, and considering that they are fifth in the Ekstraklasa table - eight points behind rivals Jagiellonia Bialystok - they may not be back in European competition next season.
As for Chelsea, they have one foot in the semi-final, and with a healthy lead to defend in London, they can afford to rest some players in the second leg.
Given that the Blues are currently fourth in the Premier League, being able to rest players next week could be vital as they battle Newcastle United, Manchester City, Aston Villa and Fulham for a spot in next-term's Champions League.
Boss Maresca will also be pleased with the performance of Sancho, who laid on two assists for Madueke, and if the former Manchester United and Borussia Dortmund man can show his talents more consistently, then he could become a crucial player for his side.
LEGIA WARSAW VS. CHELSEA HIGHLIGHTS
Tyrique George goal vs. Legia Warsaw (49th min, Legia Warsaw 0-1 Chelsea)
Chelsea work the play down the left flank and cross into the box, and though the hosts eventually clear it, Reece James recovers the ball and fires a powerful shot at goalkeeper Kacper Tobiasz, whose parry falls to 19-year-old Tryique George to tap home.
Noni Madueke goal vs. Legia Warsaw (57th min, Legia Warsaw 0-2 Chelsea)
Jadon Sancho dribbles infield from the left-hand side and picks out Noni Madueke alone in the box, and the substitute sends the goalkeeper the wrong way with a clever reverse finish into the bottom-right corner.
Noni Madueke goal vs. Legia Warsaw (74th min, Legia Warsaw 0-3 Chelsea)
Just 25 seconds after Christopher Nkunku misses a penalty, Chelsea recover the ball and play it out to Sancho on the left flank, where the winger drives forward and picks out Madueke for a close-range tap in.
It will take a lot for Legia Warsaw to come back from here!
MAN OF THE MATCH - NONI MADUEKE
Involved in the buildup to Chelsea's opener and scoring the two consecutive sealers, Madueke made the difference for Maresca's side after coming on at half time.
The Blues head back to Stamford Bridge with a dominant lead to protect, and any players that get to rest in the second leg will have the Englishman to thank.
LEGIA WARSAW VS. CHELSEA MATCH STATS
Possession: Legia Warsaw 28%-72% Chelsea
Shots: Legia Warsaw 8-24 Chelsea
Shots on target: Legia Warsaw 1-10 Chelsea
Corners: Legia Warsaw 6-8 Chelsea
Fouls: Legia Warsaw 7-5 Chelsea
BEST STATS
WHAT NEXT?
Up next for Legia Warsaw is an Ekstraklasa six-pointer against fellow European hopefuls Jagiellonia Bialystok on Sunday, while Chelsea will host relegation-threatened Ipswich Town in the Premier League on the same day.
Written by
Anthony Nolan