Rafael Benitez's hopes of winning the Europa League for a second consecutive season are in the balance after his Napoli side lost 1-0 to Porto in their last 16, first leg on Thursday.

Spaniard Benitez, who won the trophy with Chelsea last year and also lifted the UEFA Cup with Valencia in 2004, will hope Napoli can overturn the deficit in next week's return after a Jackson Martinez strike gave Porto the upper hand.

The Colombian striker, linked with a move to Naples last summer, volleyed low into the net in the 57th minute at the Estadio do Dragao after the visitors had failed to clear a corner, his shot proving too powerful for Marek Hamsik on the line.

Carlos Eduardo had an effort disallowed for offside in the first half while Pepe Reina kept out a powerful Fernando strike after the restart as the hosts, who are nine points behind leaders Benfica in the Portuguese league and recently sacked coach Paulo Fonseca, pushed forward looking for the breakthrough.

Helton saved well from a Raul Albiol header at the other end, but Porto missed a glorious opportunity to add to their lead in the latter stages, Juan Quintero hitting a loose ball against the post after a Nabil Ghilas attempt had been blocked in front of the line.

Benitez's old club Valencia appear to be all but through to the last eight after an excellent 3-0 win away to Ludogorets Razgrad in Bulgaria.

A great low strike by Antonio Barragan gave the Spanish side an early lead in Sofia, but the visitors then had Seydou Keita sent off midway through the first half for bringing down Roman Bezjak inside the area.

However, Bezjak saw his spot-kick saved by Diego Alves before Fede Cartabia and Philippe Senderos added further goals to leave the Bulgarians, the surprise package of this season's competition, staring at the exit.

FC Basel and Salzburg drew 0-0 in Switzerland, while the remaining five last 16, first leg matches were due to kick-off at 2005 GMT.

Italian rivals Juventus and Fiorentina met in a repeat of the UEFA Cup final of 1990 and Sevilla played host to city rivals Betis in Spain, with Tottenham Hotspur taking on Benfica at White Hart Lane.

The other two ties see Lyon entertain Czech champions Viktoria Pilsen and AZ Alkmaar host Anzhi Makhachkala of Russia.