Victor Osimhen and Giovanni Di Lorenzo scored to secure a deserved 2-0 victory for Napoli against Frankfurt despite Khvicha Kvaratskhelia's penalty miss.
After Kvaratskhelia had a penalty saved, Osimhen struck in the first half when he turned in Hirving Lozano's superb pass.
It got worse for Frankfurt midway through the second half as Randal Kolo Muani was sent off for a bad challenge.
Giovanni di Lorenzo then added a second, placing into the far corner.
The victory gives Napoli a big advantage for the return leg in Italy on Wednesday, 15 March.
Match Events
4' CLOSE! Rrahmani’s shot wide out
18' Great shot and save!
36' Penalty Missed! (Khvicha Kvaratskhelia)
38' Yellow Card! Min-jae Kim booked
40' GOAL! Frankfurt 0-1 Napoli (Osimhen)
56' Kvaratskhelia's shot stopped
58' Red Card! Muani sent off
65' GOAL! Frankfurt 0-2 Napoli (Di Lorenzo)
Line-ups
Frankfurt XI: Trapp, Buta, D'Dicka, Tuta, Max, Kamada, Jakic, Sow, Lindstrom, Muani, Gotze
Subs: Hasebe, Rode, Chandler, Alario, A. Toure, Lenz, Borré, Smolcic, Ramaj, Knauff, Alidou
Napoli XI: Meret, Di Lorenzo, Rrahmani, Kim, Olivera, Anguissa, Lobotka, Zielinski, Lozano, Osimhen, Kvaratskhelia
Subs: Juan, Bereszynski, Mario Rui, Politano, Gollini, Simeone, Ndombele, Elmas, Östigard, Gaetano, Idasiak