Napoli will be without Dries Mertens for its UEFA Europa League Group D clash with Midtjylland on Friday (AEDT) at the Stadio San Paolo.

The Belgium international attacker was taken off with 10 minutes to play in Napoli's 2-1 win over Fiorentina but only after providing a back-heel assist for Gonzalo Higuain's winner.

Maurizio Sarri's men have won their opening two Europa League games and arrive into matchday three in fine form, enjoying a nine-game unbeaten run in all competitions.

Midtjylland, meanwhile, have won five games in succession and top the Superliga by three points after 12 games.

Legia Warsaw and Club Brugge, with two defeats each, meet in the group's other game.

In Group A, Fenerbahce and Ajax remain winless as they meet at Sukru Saracoglu Stadium.

Question marks remain over the fitness of Nani for the Turkish host, with the former Manchester United winger set to undergo scans on Wednesday after picking up an injury in Sunday's 1-0 win over Kayserispor.

The 28 year-old has impressed after his off-season move, establishing himself as a key player in Vitor Pereira's side with four goals and four assists in all competitions.

Ajax is faring better domestically and leads the Eredivisie after nine games.

Table-topper Molde hosts Scottish champion Celtic in the other Group A fixture.

Jurgen Klopp will experience his first fixture at Anfield when his Liverpool meets Rubin Kazan, with Bordeaux playing Switzerland's Sion in Group B.

Mauricio Pochettino's Tottenham crosses the channel for its away tie against Anderlecht in Group J, with Monaco entertaining Azerbaijani side Qarabag at the Stade Louis II.

Portuguese outfit Sporting Braga will hope to extend its 100 per cent record when it hosts Marseille, while Groningen goes in search of its first points of the season in Europe when it travels to the Czech Republic to play Slovan Liberec.

Stadio Olimpico will be the scene of Lazio's meeting with Rosenborg, with last season's runner-up Dnipro facing Ligue 1's Saint-Etienne.

Group C leader Borussia Dortmund faces a tough trip to Azerbaijan to play Qabala, with Dimitar Berbatov's PAOK facing Krasnodar.

Villarreal will be hoping to record back-to-back victories when it plays Dinamo Minsk, having lost its Group E opener.

The Spanish team has some ground to make up on Rapid Vienna, which welcomes Viktoria Plzen to the Ernst-Happel Stadion.

Group K leader Schalke has won both its fixtures so far but faces its toughest challenge to date when it plays Sparta Prague.

Fellow group participants Asteras Tripolis and APOEL meet in the other tie.

Partizan, one of just seven teams to win both group games, plays Athletic Bilbao in Belgrade as Bundesliga side Augsburg faces AZ Alkmaar.

Besiktas travels to Russia to play Lokomotiv Moscow in Group H as Sporting CP greets Albanian minnow Skenderbeu.

Belenenses makes the trip to 2012-2013 semi-finalist Basel for their Group I encounter, as Fiorentina looks to close the gap on its Swiss rival when it plays Lech Poznan.