Slavia Prague scored a dramatic stoppage time equaliser to leave Arsenal’s Europa League ambitions hanging in the balance.
Substitute Nicolas Pepe thought he had earned the Gunners a slender quarter-final first-leg advantage when he broke the deadlock in the 86th minute.
But Tomas Holes headed home in the dying moments of the game from close range to give Slavia Prague a precious away goal.
The second leg in Prague takes place next Thursday (20:00 BST) and Gunners boss Mikel Arteta, despite his side conceding so late, still believes they will progress to the semi-finals.
“The mindset has to be to go there and score goals and win the game because we have to score if we want to go through,” said the Spaniard.
“I totally believe that we can go there and win the match, if not I wouldn’t be sitting here.”
Arteta stated he was in “shock” after his side’s tame 3-0 surrender to Liverpool last weekend, a performance which brought stinging criticism from both fans and pundits.
He reacted by making six changes – three of which were forced – to his starting line-up, with captain Pierre-Emerick Aubameyang the most high-profile casualty.
“Well, I cannot talk with everybody individually every week,” Arteta replied when asked how Aubameyang reacted to being dropped.
“We try to be transparent and communicate with the players as transparent as possible, for them to understand the role of the game that they have. When he came on he showed the right attitude.”
Aubameyang, who has 13 league and cup goals for his club this season but none since 6 March, cut a frustrated figure as he watched Willian, from a free-kick, clip the outside of the post before Alexandre Lacazette raced through, only to hit the bar.
Aubameyang was finally sent on after 78 minutes and made an impact as his pass allowed club-record £72m signing Pepe to race into the box and produce a composed finish past keeper Ondrej Kolar.