5 things to know about Barcelona vs. City

BARCELONA, Spain (AP) — Manchester City will need an epic comeback against Barcelona on Wednesday to reach the Champions League quarterfinals.

Barcelona won the first leg 2-0, so City will need to create plenty of goals at the Camp Nou to overturn the first-leg deficit.

The Spanish champion has lost two of its three matches since winning at Etihad Stadium, with questions swirling around Lionel Messi, Neymar and coach Gerardo Martino.

City, meanwhile, is missing coach Manuel Pellegrini to a touchline ban after the Chilean criticized the first-leg referee.

Here are five things to know about the match:

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MESSI EXPECTATIONS: In Barcelona, questions abound about Lionel Messi. He has 27 goals but has not looked his usual vibrant self, tending to drift out of games like in recent losses to Real Sociedad and Valladolid. The Argentina forward, who was also spotted throwing up on the field during a recent match, has the distractions of the World Cup in Brazil plus reports that City is offering a world record bid to sign the 26-year-old.

THE AGUERO FACTOR: If City is to mount a memorable comeback, much will hinge on the form of explosive striker Sergio Aguero. The Argentina international missed the first leg with a hamstring injury and it proved to be a huge blow to City, which was impotent up front with Alvaro Negredo playing as a lone striker. Aguero has played in City's last two matches, however, and will be looking to add to his record of 26 goals in 27 club games this season. So far he's scoreless on his return, the first time he's gone back-to-back games without netting since September. "He's so important to their attack," said Barcelona defender Javier Mascherano, who plays with Aguero for Argentina. "He's one of the top-five forwards in football. We'll try to limit his space, make it uncomfortable for him."

NEYMAR WHO?: Neymar's arrival at Barcelona has been marked by scandal rather than the samba style of play the Brazil forward promised to bring. Neymar's form has looked disjointed in recent weeks as the fallout from his transfer continues to hang over the Catalan club. Neymar has only one goal in this calendar year, and he hasn't been able to take over games when Messi struggles to carry the load, with questions over the pair's symmetry and the squad's pecking order surfacing. "Messi and Neymar haven't played together much this season," Barcelona coach Gerardo Martino said. "In the last couple of games they've clicked less, but that doesn't seem abnormal. Just because you have two of the world's best players doesn't mean they will always be in sync."

CITY CONFIDENCE: City did too little, too late, against second-tier club Wigan in the FA Cup. The players are facing a far better side on Wednesday, and the squad knows it has little time to worry about favorites. "This is one of those games where if our forwards can score then that can give us a chance," City defender Vincent Kompany said on Tuesday at the Camp Nou. "If we take control of the game, the momentum can shift. We don't need extra motivation. The message is clear, everyone knows what they must do."

BARCELONA HOT SEAT: Martino desperately needs a strong performance from his team following the dip in form since the first-leg victory. The Argentine coach's future is under discussion after back-to-back league losses on the road, especially following Saturday's 1-0 loss at relegation-threatened Valladolid. "Each of our losses has come by different reasons. We haven't played consistently," he said. "I don't think it's a problem of motivation or playing time. We just haven't been regular."