A wasteful Arsenal conceded a stoppage-time equaliser to give Slavia Prague the advantage with an away goal following a 1-1 draw in their Europa League quarter-final first leg.
Defender Tomas Holes scored a header in the 94th minute after Nicolas Pepe thought he had earned Mikel Arteta’s side a win with a goal off the bench late on.
The Ivory Coast international linked up with fellow substitute Pierre-Emerick Aubameyang, chipping a finish over the visiting goalkeeper Ondrej Kolar with four minutes of regular time remaining.
Arsenal had been wasteful up until that point, with Bukayo Saka missing a one-on-one and Willian both hitting the post, before Alexandre Lacazette passed up a huge chance, stealing the ball inside his own area and running the length of the pitch before scooping his shot on to the upright.
Slavia go into the second leg in the Czech capital just ahead in the tie and will be looking to put another British side out after already beating Premier League side Leicester and Scottish Premiership champions Rangers.
Despite dominating the first half, Arsenal struggled to impose themselves on the game and were slow in their build-up against a Slavia side well set up by boss Jindrich Trpisovsky.
Saka, making his return from injury, was by far the brightest player in the opening period and missed a huge chance when one-on-one with Kolar, with the England international cutting in from the right and putting his side-footed shot wide of the far post.
The north Londoners improved slightly for the final 10 minutes before the break and Rob Holding forced Kolar to tip the ball over the bar after getting on the end of a Cedric Soares cross on the left, but they were the only real chances for either team before the interval.
Arsenal started the half well and Saka picked up from where he left off, winning a free-kick on the edge of the area early on, which Willian clipped the post with from a difficult angle.
But the biggest chance came when Lacazette did well to win the ball off Oscar Dorley inside his own half, before running the length of the field. With only Kolar to beat, the French striker looped his effort on to the upright.
Arteta’s men had improved but were slow in the build-up, and it was only the introduction of Aubameyang and Pepe late in the game which sparked them into life.
Aubameyang almost made an instant impact from a Pepe cross, until they switched roles, with the Ivorian producing a lovely finish over Kolar to give the home team what they were sure was a winning goal.
But Slavia had one more opportunity to attack and Lukas Provod forced a save at the near post from Bernd Leno right in stoppage time to earn a corner.
Arsenal switched off from the resulting set-piece, the corner coming off the back of Pepe and diverting to Holes, who stooped low to put a header past the German goalkeeper.
The result puts Slavia just ahead of the tie with their away goal ahead of the second leg in Prague next Thursday (April 15).