As tonight's Europa League semi-final second leg in Madrid drew to the half-way mark, Arsenal had reason enough to feel confident.
Having never looked too shaken by Atletico, Arsene Wenger's side appeared to be making inroads into snatching a vital away goal.
Losing Laurent Koscielny early on through injury, Calum Chambers came on in his place. Looking comfortable against the threats of Antoine Griezmann and Diego Costa, Atletico's class eventually shone through.
Right on the cusp of half-time, a long-ball up-field from Jan Oblak was not convincingly cleared by Arsenal. Picking up on the second-ball, Thomas Partey found Griezmann, who found Costa, who crucially found Hector Bellerin unawares - 1-0.
The former Chelsea man has a habit of causing Arsenal problems from his time in the Premier League.
With 45 minutes remaining, Arsenal will need at least one goal to remain in contention of reaching the Europa League final in Lyon.
