Bayern Munich signs Borussia Dortmund star Mario Götze

Borussia Dortmund's preparations for Wednesday's Champions League semifinal against Real Madrid have been hit by news a star player wants to leave after the season.

On the eve of what it calls "the most spectacular home game in Borussia Dortmund's history," the first leg has been overshadowed by Mario Götze's decision to join Bayern Munich on July 1.

Bayern, which is triggering Götze's reported release clause of 37 million euros ($48 million), said on Tuesday it wanted to delay the announcement "out of consideration" for Wednesday's game, but Dortmund was left struggling to minimize its impact.

Götze's Facebook page quickly became a target for abusive messages from disappointed fans, and Dortmund appealed to supporters to continue to support the 20-year-old midfielder "unconditionally."

Dortmund coach Jürgen Klopp concluded Tuesday's news conference with a direct appeal to fans.

"Let's have a great night tomorrow. Leave all the negative emotions at home, come to the stadium, and let's beat Real Madrid," Klopp said.

"Borussia Dortmund is above everything. We have a chance to show it. We have the chance to show that we can deal with this extraordinarily well. We have the chance to show we can go on despite this blow. And I think we should take it."

Earlier, he said Götze was not leaving because of his teammates or the club but was joining Bayern to work with an "outstanding coach" in Pep Guardiola.

"I can't shorten myself by 15 centimeters and start learning Spanish," Klopp joked.

Excitement has been palpable in Dortmund for another clash between last season's German and Spanish champions. Dortmund beat Madrid 2-1 at home in the group stage, and claimed a 2-2 draw away before topping Group D.

"We've a lot to gain, nothing to lose," said Dortmund chief executive Hans-Joachim Watzke.

Some Dortmund fans queued over two nights for tickets after a limited number were made available on Tuesday, and police had to intervene after scuffles broke out when suspected ticket scalpers sent their own people to try to jump the queues. All 65,829 tickets for the game are sold out.

Klopp hopes their enthusiasm hasn't diminished.

"If there's someone who hasn't realized by tomorrow how important this is to us all, how much we've dreamed of this, then, really, they shouldn't come," he said.

Dortmund, the only undefeated side left in the competition, completed a remarkable comeback in the quarterfinals with two goals in injury time to defeat Malaga 3-2, and is looking for a hat trick of home victories against Spanish opponents this season.

The sides last met in the semifinals in 1998, on Dortmund's last appearance at this stage, when Madrid prevailed 2-0 on aggregate to dethrone the defending champion.

Dortmund is aiming for just its second European Cup final, while Madrid has its 13th in sight. Jose Mourinho's side has lost three semifinals since it last won the trophy in 2002, crashing out to Bayern on penalties last year.

Madrid trails Barcelona in the Spanish league and has been focusing on the Champions League in what is likely Mourinho's last season in charge.

"We are going to Germany to win so we can return to the Bernabeu with guarantees to try and reach the final," said Madrid forward José Callejón.

The Spanish side had a costly 3-1 victory over Real Betis on Saturday when midfielder Luka Modrić and defender Marcelo had to go off with injuries. French striker Karim Benzema, who scored one goal and set up another, was also favoring his right leg and had to be substituted late.

Mourinho rested his first-choice defense, with only Raphaël Varane and Pepe seeing minutes as substitutes. Playmaker Xabi Alonso was also rested.

Both Modric and Benzema made Madrid's 23-man squad but Marcelo was omitted.

The visitors will look to Cristiano Ronaldo to maintain his fine scoring record. The Portugal star leads the Champions League with 11 goals and is within reach of the single-season record of 14 goals held by Lionel Messi. Ronaldo has scored 50 goals for Madrid in all competitions this season.

"There are only a few in the world who can match him. Thankfully (Poland defender) Lukasz Piszczek is one of them," said Dortmund midfielder Nuri Sahin, who endured a frustrating time as a Madrid player. "He won't be able to stop him alone, we have to work as a team."

Dortmund's Robert Lewandowski, another reported Bayern target, has scored in 12 consecutive Bundesliga matches.

Dortmund dominated the past two domestic seasons but surrendered the Bundesliga title to Bayern this month. The last time Dortmund surrendered back-to-back titles to Bayern was in 1997, when it atoned by winning the Champions League.

Bayern has provided even more motivation with the Götze transfer.