Diego Simeone’s side had every right to feel nervous arriving in Belgium, facing a Brugge side that had lost only three of their previous 21 European home games and had also failed to score against them in the last three H2Hs.
However, they took just seven minutes to the end that latter run, after Joaquin Seys was penalised for handball inside the box following a VAR review.
From the subsequent penalty, Julián Alvarez confidently beat a motionless Simon Mignolet.
Nevertheless, the hosts’ response was encouraging, and Atleti were indebted to Jan Oblak for pushing away Nicolò Tresoldi’s speculative strike from distance amidst a sustained spell of pressure.
Oblak was then called into another fine save to keep out Raphael Onyedika’s long-range effort, but the LaLiga side doubled their advantage in first-half stoppage time. Antoine Griezmann flicked on Marcos Llorente's corner, and Ademola Lookman turned the ball home from point-blank range.
The 2-0 scoreline was a harsh reflection on Brugge’s first-half endeavours, but they halved the deficit seven minutes after the restart thanks to Onyedika.
He was alert to a loose ball inside the box after Oblak made a superb stop to keep out Tresoldi’s initial header, applying a poacher’s finish to prod the ball over the line.
A remarkable turnaround was then complete just past the hour mark when Tresoldi's outstretched leg poked Mamadou Diakhon’s cross past Oblak.
Simeone responded by freshening up his forward line with the introduction of Alexander Sørloth, who almost made the desired quick impact when his header from Koke’s searching ball into the box clipped the bar.
The Norwegian was proving to be a handful for the Brugge defence and played a key role in Atleti regaining their lead. Joel Ordóñez panicked with the frontman in close proximity, and inadvertently diverted Llorente’s cross into his own net.
But just when Ivan Leko’s men looked to be heading towards an undeserved defeat, Christos Tzolis' brilliant angled finish ensured the aggregate score remained level before next Tuesday’s second leg in Madrid.
This result extends their unbeaten run against Spanish teams to six games (W2, D4), while Simeone’s men will be wondering what might have been, having won just one of their last five games on the road across all competitions (D3, L1).
Flashscore Man of the Match: Raphael Onyedika (Club Brugge)