Liverpool travel to Spain for their quarter-final first leg against Real Madrid on Tuesday night.

The two sides will feature mouth-watering attack units and some makeshift defences due to injury, so there are hopes for an open contest at the Estadio Alfredo Di Stefano.

Here the PA news agency takes a look at three key battles which should help determine the outcome.

Raphael Varane v Mohamed Salah

With Sergio Ramos missing through injury, Raphael Varane will be needed to lead the Madrid defence against Liverpool's three-pronged attack. Nacho Fernandez has proven a reliable fill-in during the course of the season but there could also be a role for the 23-year-old Brazilian Eder Militao, who has made only eight appearances this season, and started against Eibar at the weekend. Zidane may well go with a 3-5-2 formation, having been willing to switch things around depending on which players are available, but however they line up, much of the onus to control Liverpool's attacking players will fall on the shoulders of Varane.

Georginio Wijnaldum v Toni Kroos

With both attacking units looking to get the better of the understrength defences, the difference in the game could be the battle for possession and to get service into the forwards. The fight for control in the middle of the park could come down to these two – and it is a match-up which may soon be seen in LaLiga as Wijnaldum continues to be linked with a move to Barcelona when his Liverpool contract expires in the summer. Kroos is the more creative of the two, with the German also comparing favourably in terms of his ability to break up play, but Wijnaldum's tireless work-rate will be invaluable to the Reds.

Ozan Kabak v Karim Benzema

Though Liverpool's problems at the back have been well documented, there have been positive signs in recent weeks. January arrival Kabak made a shaky start to his Anfield career but has steadily improved and has formed a decent partnership with Nat Phillips – with the pair yet to concede a goal as a starting duo. That record will get its stiffest examination yet on Tuesday night against Benzema, who has scored 24 goals in 33 games for Madrid this season, and has nine goals in his last seven. The Frenchman is far from the only threat they will face, but keeping him quiet will go a long way towards getting Liverpool the sort of result they want in Spain.