Arsene Wenger's Arsenal reign looks likely to end on a sour note after 10-man Atletico Madrid grabbed a late equalizing away goal through Antoine Griezmann. Marseille made light work of Salzburg in the other semifinal.
Arsenal 1 - 1 Atletico Madrid
(Lacazette 61' - Griezmann 82')
A late Antoine Griezmann strike handed Atletico Madrid a huge advantage, after a characteristic backs-to-the-wall performance that casts serious doubt over a happy ending for Arsene Wenger's reign at Arsenal.
The hosts started at a frantic pace and Atletico struggled to cope with the tempo and the movement of the men in red. Sime Vrsaljko was the man that paid the price for the Spanish side's early failure to adapt, the Croatian fullback picking up a pair of quick bookings to be dismissed after just 10 minutes.
Even before that dismissal, Alexandre Lacazette and Danny Welbeck had passed up opportunities for Arsenal, and the chances continued to flow for the Londoners after Atleti boss Diego Simeone was sent to the stands for furiosly protesting a 12th minute decision.
Laurent Koscielny, Jack Wilshere and Nacho Monreal all had golden opportunities to make Simeone's night even worse but all fluffed their lines. Buoyed by their lucky escape, the visitors started to grow in to the game, and almost took the lead just after the half hour mark, when David Ospina was forced in to a smart save by a fierce Griezmann drive.
The 2012 winners boast an impressive European pedigree over the last decade or so and drew on their experience to take the sting out of Arsenal as the half wore on, with a last-ditch tackle here and a tactical foul there ensuring the sides went in level at the break.
The second period saw Atleti continue attempting to use their experience, eating up the clock even in the early stages of the second half. But they were finally undone by the simplest of goals, Lacazette rising highest at the back post to nod home Wilshere's left-wing cross.
Lacazette flashed a header just wide of the post after 69 minutes as Arsenal continued to pile on the pressure but failed to make it pay. Almost inevitably they were punished by one of Atletico's rare ventures in to opposition territory. Arsenal appealed for a foul on Welbeck as Griezmann out-muscled Koscielny before beating Ospina at the second attempt as Shkodran Mustafi slipped.
There was still time for Jan Oblak to make a strong save from Aaron Ramsey but, ultimately, Arsenal will be left ruing their missed chances, while Wenger looks increasingly likely to end the last of his 22 seasons in London without a trophy.
Marseille 2 - 0 Red Bull Salzburg
(Thauvin 15', Njie 63')
An inspired display by hometown hero Dmitri Payet helped Marseille take a step closer to their first major European final for 14 years.
The French side took the lead in the 15th minute through a familiar supply line. Payet’s whipped free kick cleared the Salzburg defense and goalkeeper and was bundled in at the back post by Florian Thauvin, who has been directly involved in 34 goals for the French side this season.
Payet, a star of Euro 2016, was a constant thorn in the Austrian club's side and almost created a second for Lucas Ocampos before the break. The former West Ham man's classy display was rewarded with yet another notch on his assist post after the break as substitute Clinton Njie finished off a smart move less than three minutes after coming on. He's now laid on 17 assists in his 36 starts to date.
Surprise package Salzburg will require something of a miracle to make their bow in a mjor European showpiece. The second legs of both ties are next Tuesday.