Bayern v Real Madrid -- five key battles

Bayern Munich host Real Madrid in Wednesday's blockbuster Champions League quarter-final first leg. Here are five key battles to look out for in the Allianz Arena clash:

Robert Lewandowski v Cristiano Ronaldo

Lewandowski netted twice in Bayern's 4-1 thrashing of Borussia Dortmund to take his goals tally for the season to 38, but he gave his side a scare when he came off clutching his shoulder in the second half.

The Polish striker is expected to be fit though and Real fans know all about Lewandowski, who scored all four goals for ex-club Dortmund in their 4-1 win in the 2013 Champions League semi-finals.

Ronaldo has finished as the Champions League's top scorer in each of the past four seasons, but the Portugal star is on a six-game run without a goal in Europe -- his longest drought in a Real jersey.

The world player of the year's return of 26 goals in 36 games this term is modest by his standards, but he has tormented Bayern in the past with four goals in as many games against the German giants.

Thiago Alcantara v Luka Modric

Much of the battle for midfield superiority will fall upon the creative talents of Thiago and Modric trying to break down the opposing defence.

Thiago has plenty of experience against Madrid -- he was the one player ex-Bayern coach Pep Guardiola insisted on poaching from Barcelona when he arrived in 2013 -- and has been outstanding in his best season since moving to Germany.

Modric's ability to link defence and attack has made him Madrid's most important player since Zinedine Zidane took charge 16 months ago.

However, the Croatian has suffered a slight dip in form over the past month as the strain of Madrid's participation in six competitions this season has started to take its toll.

Xabi Alonso v Toni Kroos

Kroos's transfer from Bayern to Madrid fresh from winning the World Cup in 2014 provoked Alonso's move in the other direction and both clubs have reaped the benefits.

At 35, former Spain international Alonso is enjoying one final season before retiring in June.

His lack of pace has seen him accused of slowing down Bayern's attack, but his long-range passing ability can still quickly turn defence into attack.

Kroos, 27, has become a set-piece assist machine at the Bernabeu. His free-kick that set up Pepe's opener in the Madrid derby was already his 15th assist of the campaign.

Manuel Neuer v Keylor Navas

Between the sticks the advantage should clearly be with Bayern, as Neuer looks set to return after recovering from a minor foot operation 10 days ago.

The Germany number one resumed training on Monday, with reserve Bayern keeper Sven Ulreich likely to give way after filling in for the past three games.

In Neuer's absence Bayern suffered a rare Bundesliga defeat, losing 1-0 at Hoffenheim last Tuesday, and Carlo Ancelotti will be relieved to see the World Cup winner back in the line-up.

Navas's days as first choice at the Bernabeu seem numbered after a series of high-profile mistakes this season. Madrid haven't kept a clean sheet with Navas in goal since January.

Jerome Boateng v Sergio Ramos

With so much attacking talent on show, two of Europe's top defenders will be stretched to their limits and whoever provides more resistance could prove the key to the tie.

Boateng, Germany's footballer of the year for 2016, has only just returned from shoulder surgery in December.

However, his presence will be needed more than ever with international teammate Mats Hummels out with an ankle injury he suffered in training on Sunday.

Real's heroic captain Ramos has become synonymous with huge Champions League goals -- including two when the sides last met in Munich three years ago.

However, with Pepe and Raphael Varane sidelined, his experience will be vital next to Nacho at the heart of the Madrid defence.