Enzo Maresca admitted Chelsea had "disrespected" their opponents as they were booed off after limping into the Conference League semi-finals 4-2 on aggregate despite a 2-1 defeat to Legia Warsaw at Stamford Bridge.
Much like Sunday's draw with Ipswich, the Blues started brightly on home soil before falling behind to the visitors' first attack of the night, with Tomas Pekhart beating Filip Jorgensen from 12 yards after the goalkeeper had brought him down inside the area.
Legia head coach Goncalo Feio had said his side would dare to dream of an unlikely comeback if they took the lead in London.
Those fantasies almost moved a step closer to reality as Ryoya Morishita narrowly missed the far post with a golden chance to add a second soon after when played in behind.
- As it happened | Teams | Match stats
- Europa Conference League fixtures
- Not got Sky? Get Sky Sports or stream with no contract on NOW 📺
Having fielded questions about fan frustrations in his pre-match press conference, Maresca again was subjected to murmurs of discontent until Marc Cucurella, Chelsea's top Premier League scorer in 2025, came to the rescue again before half-time.
The left-back netted his fourth goal of the calendar year by tapping home Jadon Sancho's cross to relieve the growing angst around Stamford Bridge.
But the Blues would again be frustrated after the break, when Claude Goncalves' half-volley from a corner was bundled home from close-range by Steve Kapuadi, to again give Legia a glimmer of hope.
Player ratings:
Chelsea: Jorgensen (4), Acheampong (5), Tosin (5), Badiashile (6), Cucurella (7), James (6), Dewsbury-Hall (6), Sancho (7), Palmer (6), Nkunku (5), Jackson (5).
Subs: George (6), Gusto (5), Madueke (6), Neto (n/a).
Legia Warsaw: Kovacevic (7), Pankov (6), Ziolkowski (7), Kapuadi (7), Vinagre (5), Oyedele (6), Elitim (6), Goncalves (8), Morishita (7), Pekhart (7), Luquinhas (7).
Subs: Chodyna (5), Szczepaniak(5), Augustyniak (5), Jedrzejzyk, Bichakhchyan (n/a).
Player of the Match: Claude Goncalves.
They may rue referee Alejandro Hernandez's decision not to award them a second penalty of the night soon after, when Jorgensen again appeared to clean out Luquinhas after spilling a cross - though VAR Guillermo Cuadra was similarly unconvinced.
That left Chelsea to see out their aggregate victory in relative comfort, despite an unconvincing performance on the night, with more boos from the stands at the final whistle following a second unconvincing home performance in four days.
After the game, captain Reece James suggested Chelsea had disrespected the Conference League with their performance, but Maresca felt it was more a case of complacency with the size of the Blues' first-leg lead.
"Not the competition, but maybe the other team tonight," he said. "We respect the competition all season, probably tonight because of the first result you can manage the result in the wrong way. For sure, Reece is right but it's more than the competition, the opposite."
The Blues will face Djurgardens in the semi-finals, with the two legs played on May 1 and May 8.
Analysis: Maresca can't keep ignoring growing boos forever
Sky Sports' Ron Walker at Stamford Bridge:
"It was probably complacency which led to a defeat which ultimately costs little more than pride for Chelsea's season, but for Enzo Maresca it may eventually prove more costly.
"His pre-match press conference on Wednesday did not give the feel of a team 3-0 up from the first leg, as he spent more time fielding questions on whether his style could ever be successful at Stamford Bridge and if he had heard the fans booing during Sunday's draw with Ipswich.
"He said he was too busy focusing on the game to notice those frustrations but there is no chance he missed the catcalls from around Stamford Bridge at full-time after this embarrassing loss. It is less about this defeat in isolation; things have been turning against him for some time, it is a cumulative effect.
"Indifferent results in the second half of the season coupled with a perceived dull style of football has not endeared the Chelsea boss to the club's fans. That lack of credit in the bank means any mitigation about motivation after that first-leg victory will not wash with many.
"The biggest worry is that Maresca carried this tag when he took the job. Leicester were less upset about losing their manager last summer than you would expect of a Championship winner after a similar drop-off that Chelsea fans have seen this season.
"The Blues are only a point off the top five but there is little belief they will reach the Champions League next season now.
"Fulham on Sunday is a far bigger game for Maresca and Chelsea, and losing that would have far bigger consequences in the stands - and may start to turn heads in the boardroom too."
Maresca looks for positives despite defeat
Chelsea head coach Enzo Maresca:
"Overall, the good thing is we can rotate players, we don't have injuries, and that was the main target because during the season we have had many injuries in important moments.
"The idea was for Nicolas [Jackson] and [Cole] Palmer, especially with Nico who has had two months out, to build his condition and give him 45 minutes.
"The environment was good tonight. I didn't see any bad moments from the fans. I said already after the last game we need to engage them, and that's what we have to do."
Feio: We knew stadium was not fully behind team
Legia Warsaw head coach Goncalo Feio:
"We knew at the moment this is not the loudest stadium and the last league games haven't helped with this. We knew we would feel the presence of our fans.
"I am proud of the team, we wanted to change our performance after the last game. I knew we could do better than that, however you need to have belief and put it into practice.
"The team showed great character and personality, even against such an opponent who hasn't lost until now."