Athletic Bilbao's Raul Garcia headed the only goal of a near-farcical first leg of their all-Spanish tie with Valencia in the Europa League's last 16.
Garcia glanced in from a free-kick after 20 minutes to give Bilbao the least they deserved from a match played in torrential rain and on a saturated pitch at San Mames.
Current champions Sevilla played out a goalless draw at Basel after having Steven Nzonzi sent off three minutes from time for a second bookable offence.
The Spanish side had dominated the second half, with Basel goalkeeper Tomas Vaclik making good saves to deny Nzonzi, Kevin Gameiro and Yevhen Konoplyanka. Basel's best opportunities were spurned by Marc Janko and Birkir Bjarnason.
Shakhtar Donetsk claimed a 3-1 win over Anderlecht in Lviv. Two goals in the space of three minutes from Taison and Olexandr Kucher gave the Ukrainian side the lead during a first half in which they also hit the post through Eduardo.
Anderlecht rallied after the break and pulled one back through Frank Acheampong but Eduardo's 79th-minute effort ensured a healthy lead for Shakhtar.
Mehmet Topal scored an 82nd-minute winner as Fenerbahce beat Braga 1-0 in Istanbul. The decisive strike came just moments after Fenerbahce goalkeeper Volkan Demirel made a fine save to deny Josue at the other end.
Cedric Bakambu scored in either half to give Villarreal a 2-0 victory over Bayer Leverkusen and leave them in charge of their last-16 tie.
The forward broke the deadlock four minutes in and doubled the Yellow Submarine's advantage nine minutes after the restart to ensure they secured a healthy lead ahead of the return leg in Germany in seven days' time.
And Leverkusen will be without Tin Jedvaj for that contest after he was dismissed for two yellow cards, the second coming in the penultimate minute of stoppage time for a deliberate handball.
Meanwhile, Sparta Prague drew 1-1 with Lazio in Prague after Marco Parolo's second-half strike cancelled out Martin Frydek's 13th-minute opener for the hosts.
Elsewhere, Marco Reus scored twice as Borussia Dortmund overpowered Tottenham 3-0 at Signal Iduna Park, where the German side dominated.
Pierre-Emerick Aubameyang, who earlier had an effort disallowed, headed the opener after 30 minutes, with Reus volleying home a second from close range just after the hour and and adding his second with a neat finish 10 minutes later.
Daniel Sturridge gave the hosts the lead after 20 minutes from the spot after Memphis Depay brought down Nathaniel Clyne in the box, and Roberto Firmino added another goal in the second half.