LONDON (AP) -- With at least $12 million guaranteed for Champions League participants, it's little wonder the final playoffs for the group stage are so tight.
Going into the second legs this week, no team leads by more than a goal and half of the 10 games are level.
Arsenal, which drew 0-0 at Besiktas last week, has an enviable record of playing in the group stage every year since the 1998-99 season to protect. Former champions Celtic and Porto at least managed to score potentially valuable away goals.
Here are five things to know about the second legs of the playoff round:
The task is clear for Arsenal on Wednesday at the Emirates Stadium. Progress is only possible by winning the match or forcing a non-scoring draw and triumphing on penalty kicks. Arsene Wenger will miss midfielder Aaron Ramsey, who was sent off in Turkey and has scored in both Premier League matches this season. Arsenal's attacking struggles were highlighted at Everton on Saturday when only late goals - from Ramsey and Olivier Giroud - recovered a draw.
''When you don't score people are critical about goals and I agree with them, but we had chances and having watched the game again I believe we had the chances against Besiktas,'' Wenger said. ''Joel Campbell can contribute to that. At the moment he has not got his chance, but he will get it.''
LEVERKUSEN ON A HIGH
Goals weren't a problem for Bayer Leverkusen in its away leg, beating FC Copenhagen 3-2 in the highest-scoring game of the round. Coupled with a winning start in the Bundesliga, it's been the perfect start for new coach Roger Schmidt. The 47-year-old German took charge after a successful spell at Austrian champion Salzburg and has quickly molded Leverkusen into a cohesive unit. Now the side is bidding to reach the Champions League for the second straight season on Wednesday, and then go further than the round of 16 this time.
Athletic Bilbao showed last season it could cope after the exit of two key players - Fernando Llorente and Javi Martinez - by finishing fourth in the Spanish league. That gave Bilbao this shot at the Champions League group stage, which the team can reach by holding on to the 1-1 draw achieved at Napoli last week.
Coach Ernesto Valverde is trying to fill the void left by playmaker Ander Herrera after his departure to Manchester United in the offseason. The task has fallen on Iker Muniain, the 21-year-old attacking midfielder with his difficult-to-decipher intentions when the ball is at his quick feet. Muniain scored at Napoli to give Bilbao the away-goal advantage heading into Wednesday's second leg at San Mames stadium.
''We have a very difficult match on Wednesday when any lapse in concentration can cost us dearly,'' said Valverde, whose side lost the weekend domestic opener at Malaga after a defensive blunder.
Scottish champion Celtic is making the most of its reprieve in the Champions League. The 1967 European Cup winners owe their appearance in the playoffs to UEFA's legal department after losing home and away to previous opponent Legia Warsaw. Celtic advanced when the Polish champion was punished for fielding a suspended player. Leaving Slovenia with a 1-1 draw at Maribor gives Celtic the edge going into the second leg on Tuesday.
Porto will to play in the group stage for a 19th time if the 2004 champions can protect a 1-0 advantage over Lille at home on Tuesday. Zenit St. Petersburg takes the same result into its game at home to Standard Liege on Tuesday, while Steaua Bucharest is at Ludogorets Razgrad with the same lead the following night. Malmo must overturn a 2-1 deficit against Red Bull Salzburg on home soil to reach the group stage for the first time. APOEL, a surprise quarterfinalist three seasons ago, hosts Aalborg after drawing 1-1 in Denmark. BATE Borisov is also taking a 1-1 draw back to Belarus against Slovan Bratislava.
Associated Press Writers Joseph Wilson in Barcelona, Spain, and Ciaran Fahey in Berlin contributed to this report.