With hopes of a fourth consecutive Spanish league title fading, Barcelona is turning its full attention to defending its European crown - which is bad news for Bayer Leverkusen.

Both sides are having domestic troubles going into their meeting in Tuesday's Champions League round of 16 first-leg match, but it is arguably Barcelona which has more to prove.

Saturday's 3-2 loss at Osasuna, coupled with Real Madrid's 4-2 win over Levante on Sunday, left the defending Spanish champion 10 points behind its bitter rival, which has dropped only eight points all season.

Barcelona coach Pep Guardiola suggested Monday night that his side was struggling under the weight of expectation.

''You have the feeling that if we don't win the Champions League it's a failure,'' he said, before rejecting the notion of European success as a ''replacement drug'' to atone for failure in the league.

''The Champions League is always difficult at this stage. We know how close it can be. That's why I don't understand this argument,'' Guardiola said.

Barcelona defender Dani Alves put Saturday's setback aside, preferring instead to look ahead.

''Of course the points difference is big, but we're in a different competition now and we have to concentrate on that,'' the Brazilian said.

Leverkusen has problems of its own, having claimed only one win in its last seven games while the club is at odds with its midfielder Michael Ballack.

The former Germany captain hasn't played for Leverkusen since managing director Wolfgang Holzhaeuser described his transfer back to the club as a ''failure.''

Leverkusen failed to win any of the three games in which Ballack remained an unused substitute, but any thoughts Leverkusen coach Robin Dutt may have had of giving the 35-year-old a final hurrah on the big stage were dashed Sunday, when Ballack tore a calf muscle in training.

Ballack's injury is just the latest to affect Dutt's side. Winger Sidney Sam and Switzerland striker Eren Derdiyok were both ruled out with foot injuries, the latter after stepping on broken glass in his bathroom last week.

Leverkusen missed their attacking presence in the 1-0 loss Borussia Dortmund on Saturday, when the side looked anything but inspired.

''On Tuesday, it could be a tick more difficult,'' Dutt said.

Leverkusen is currently sixth in the Bundesliga on goal difference.

''We're not dreamers but realists,'' said Leverkusen sporting director Rudi Voeller. ''We want to make sure of the Europa League place and secure international football that way.''

Leverkusen captain Simon Rolfes described Tuesday's match as ''a classic David vs. Goliath game.''

Still, his side hasn't given up hope of progressing to its first Champions League quarterfinal since reaching the final in 2002, when Ballack was in his first stint at the club.

''Miracles are always known to happen,'' Holzhaeuser said.

Dutt, too, is drawing on positive thoughts.

''You always think you've experienced everything in football. But you haven't experienced anything yet. This story also has to be written first,'' said the Leverkusen coach.

Nonetheless, Dutt is aware of the monumental task his side faces.

''Barcelona are better than Spain. You only have a chance when you get your tactics perfect and Barcelona have a bad day,'' he said, before joking that a 5-0 win would suit Leverkusen just fine.

Barcelona captain Carles Puyol insisted that the Catalans were focused on all competitions after enduring only their second loss of the season.

''We'll fight to the end in all three competitions, whoever thinks the opposite is wrong,'' he warned on Sunday.

Puyol said the players were ''not machines'' that could be connected one day and disconnected the next.

''We have to give everything every game, and we'll do this until the end of the season.''

Guardiola spared Andres Iniesta and Xavi Hernandez from Osasuna's frozen pitch with Tuesday's game in mind.

Cesc Fabregas made only a late appearance from the bench meaning the visitors will have an almost fully fit squad, apart from the long-term absences of David Villa and Ibrahim Afellay.

Midfielder Sergio Busquets was the main doubt after missing two games but traveled with the team to Germany.

''He completed most of (Monday's) training,'' Guardiola said. ''We'll see how he progresses and make a decision then.''

Guardiola has been using a number of reserve players recently, with wingers Isaac Cuenca and Cristian Tello making significant impacts, while midfielder Sergi Roberto started on Saturday alongside Thiago Alcantara.

But all signs point to the return of Xavi and Iniesta on Tuesday, which could help to spark a sub-par Lionel Messi to reach his own lofty heights.

''Our target is to play to get to the quarterfinals and then take it step by step,'' Guardiola said.

He played down Barcelona's chances of becoming the first side since AC Milan in 1990 to successfully defend its European crown.

''Times have changed since Milan last did it. Nobody else has done it since, so it shows how difficult it is,'' he said.

Instead, Guardiola - a former Barcelona midfielder - pointed to what his players had already achieved.

''These guys are part of the history of football and they're going to try to win it again,'' he said.

Leverkusen is happy to play a part in that history.

''We've been looking forward to this game for weeks, for the fans and for our young players to play against the world's best team,'' Voeller said. ''Of course it's a dream.''

Voeller, a former Germany striker and coach, said his side would ''of course'' attempt to get a positive result against Barcelona.

''But they aren't quite so bad. You look at them sometimes and say, 'Ah, how lovely they play.' For the players it's great to see at first hand how they do it and why they are so good.''


AP Sports Writer Paul Logothetis contributed from Madrid.