Genk were the biggest winners of the night, putting five past Belgian rivals Gent, with Lyon well on top in their round of 16 tie with Roma and Rostov on level terms with Manchester United.
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Five of the UEFA Europa League round of 16 ties have a leader after Thursday night's first legs – watch highlights of every game.
Thursday's round of 16 first legs (click for individual match highlights)
APOEL 0-1 Anderlecht
Celta 2-1 Krasnodar
Gent 2-5 Genk
København 2-1 Ajax
Lyon 4-2 Roma
Olympiacos 1-1 Beşiktaş
Rostov 1-1 Manchester United
Schalke 1-1 Mönchengladbach
The evening got off to a fast start thanks to Rasmus Falk's opener for København after just 28 seconds. Though the Danish side's keeper Robin Olsen subsequently conceded at home for the first time in 999 minutes, Ståle Solbakken's team went on to win and are now 19 matches unbeaten in all competitions. Rostov were responsible for another surprise result, securing a draw to take to Old Trafford courtesy of Aleksandr Bukharov's equaliser.
Elsewhere, Nabil Fekir – top of the FedEx Performance Zone rankings – was among Lyon's scorers against Roma, while 36-year-old Esteban Cambiasso found the net for Olympiacos against Beşiktaş.
Bundesliga rivals Schalke and Gladbach shared the spoils in the second of their three meetings in the space of 13 days, with Genk coming out on top away to fellow Belgians Gent. Another club to lose on their own patch were APOEL, hitherto undefeated on home soil in 33 fixtures.
The final twist of the night came in Vigo, substitute Claudio Beauvue's 90th-minute header earning Celta a slender advantage against Krasnodar.