Despite Chelsea sitting just one point adrift of the Premier League’s fifth and final Champions League qualification spot - and possessing a 3-0 lead in this tie from the first leg - all was not well amongst the Blues supporters after a poor 2-2 draw with Ipswich continued a sequence of poor domestic results.
Enzo Maresca duly fielded a stronger starting XI than expected, which included Cole Palmer, Nicolas Jackson, Marc Cucurella and Reece James.
The Blues started well, with Palmer firing wide from a good position before Legia goalkeeper Vladan Kovacevic saved from Christopher Nkunku and the England international in quick succession.
But Legia soon found a foothold in the game and won a penalty inside 10 minutes, when Filip Jorgensen felled Tomas Pekhart.
While the Dane did get a hand to the Czech striker’s subsequent spot-kick, it was not enough to prevent it from finding the bottom corner.
The visitors gained confidence from that opener, and roared on by a vocal travelling contingent, they almost went two up when Ryoya Morishita fired narrowly wide of the post.
Chelsea did eventually improve, though, and were back on level terms shortly after the half-hour mark when Cucurella tapped home.
The Spaniard then thought he had completed the turnaround shortly after, but his finish from close range was ruled out for offside.
Legia returned to the field of play with renewed vigour and, after Jorgensen denied Claude Goncalves, the Polish outfit restored their lead when Steve Kapuadi headed in from inside the six-yard box following a corner.
That goal did at least spark Chelsea partly into life, with Jadon Sancho forcing Kovacevic into action before substitutes Noni Madueke and Tyrique George had efforts cleared off the line, keeping Legia’s unlikely lead on the night intact.
Maresca and his team will try to take the positives from this encounter. In the immediate term, they remain on course for silverware and could still become the first club to win all three of UEFA’s currently active club-level major tournaments.
Still, given their status as overwhelming favourites to prevail overall, such a loss will feel bitterly disappointing. Meanwhile, Legia’s European journey this term may have come to an end, but they can hold their heads high after winning on English soil for the first time ever.
Flashscore Man of the Match: Tomas Pekhart (Legia Warsaw)