Marek Hamsik... Champions League provides different dimension.

Napoli’s first game of the season could also be one of their most difficult and important as they host Spain’s Athletic Bilbao in the first leg of their Champions League play-off tie tonight.

Arsenal, who visit Besiktas, will be aiming to reach the lucrative group stage for the 17th consecutive season while, at the other extreme Slovan Bratislava, Ludogorets Razgrad and Malmo are all trying to qualify for the first time.

Millions of euros are at stake for the clubs involved in this week’s 10 matches thanks to the huge appearance fees, performance bonuses and television money handed out by UEFA to those who reached the group stage.

Last season, UEFA awarded each of the 32 teams 8.6 million euros just for taking part in the group stage, with more thrown in for wins and draws.

Napoli’s participation last season brought them 38.6 million euros, including four million in the so-called performance bonuses and 26 million euros their share of the television market pool.

Failure to beat Athletic Bilbao, Europa League runners-up in 2012, could put immediate pressure on Napoli coach Rafael Benitez, whose debut season in the 2013-14 campaign was regarded as only satisfactory.

A third place Serie A finish and the Coppa Italia title were the bare minimum expected from the Spaniard at Italy’s biggest-spending club who performed only in fits and starts last term, repeatedly dropping precious Serie A points against lower-placed opposition.

“Those two matches can shape a season because it’s true that the Champions League provides a different dimension to the club, the city and to us players,” said Napoli forward Marek Hamsik.

“Among the five possible opponents, with Athletic we have been landed with the most difficult,” warned Benitez.

“They’re a team who play good football and, at home, the 50,000 at San Mames give them a big push. It will be a very good, and very intense game.”

Arsenal will have played one Premier League match before they visit Besiktas in Istanbul today, although last season’s 5-0 aggregate win over Fenerbahce suggests they should be able to cope with the Turks.

Slovan Bratislava host Belarus champions BATE Borisov tomorrow as they attempt to emulate MSK Zilina, MFK Kosice and Petrzalke by representing Slovakia in the group stage.

Denmark have a chance to have two teams in the group stage for the first time

Ludogorets Razgrad begin their attempt to become only the second Bulgarian side to qualify when they visit former European champions Steaua Bucharest today.

Malmo, runners-up in the old European Cup, visit Austrian champions Salzburg, hoping to become the first Swedish team to qualify for 14 years.

Salzburg themselves have not qualified since the takeover by the Red Bull energy drinks manufacturers in 2005 although they did qualify in 1994-95, back in the old days when they still played in violet and white.

Belgium midfielder Axel Witsel will return to his old club with Zenit St Petersburg when the Russians, led by Portuguese coach Andre Villas-Boas, visit Standard Liege tomorrow.

Ambitious Zenit St Petersburg, whose new signings included Argentina World Cup defender Ezequiel Garay, have made a flying start to the Russian Premier League, winning their first four games and beating Torpedo Moscow 8-1 in the process.

Group stage regulars Porto, the club where Villas-Boas made his name, have a tough trip to Lille while Celtic, who like Porto are former European champions, visit Slovenian champions Maribor

Denmark have a chance to have two teams in the group stage for the first time as FC Copenhagen host Germany’s Bayer Leverkusen with Aalborg at home to APOEL, surprise quarter-finalists two seasons ago.

The second legs of the play-offs round will be played on August 26 and 27 with the draw for the group stage taking place in Monaco on August 28.

Champions League, play-offs

Second legs: August 26/27.