Spanish giants Real Madrid and Barcelona have mountains to climb this week as both look to overturn daunting deficits in their UEFA Champions League semi-final deciders.

Los Merengues lost 4-1 to Borussia Dortmund and Barça went down 4-0 away to Bayern Munich, with the victors signalling a dramatic resurgence in German club football. The Bundesliga duo will now seek to use all their experience to complete their missions and book places in the Wembley final on 25 May.

This week's fixtures
Semi-final, second legs:

Tuesday 30 April
Real Madrid-Borussia Dortmund (first leg: 1-4)

Wednesday 1 May
Barcelona-Bayern Munich (first leg: 0-4)

Real Madrid-Dortmund

The match
Hosts Madrid face an uphill task if they are to avoid a third semi-final exit since 2002, particularly given their record against Dortmund this season. The Spanish side have suffered two defeats and needed a late equaliser to scrape a draw in their other meeting, conceding eight goals in those games and registering four.

They trail their German rivals by a daunting three goals ahead of Tuesday's game but were at least able to raise morale with a 2-1 derby win at Atletico Madrid on Saturday, consolidating second place in the Liga despite resting a number of players. Karim Benzema and Angel Di Maria performed well to remind coach Jose Mourinho of their potential, and there can be no doubt that Madrid boast the talent and experience to turn things around, particularly in front of a vibrant Santiago Bernabeu crowd that has witnessed comebacks aplenty in the past.

Dortmund look unlikely to be intimidated, however, having grown in stature since topping the so-called Group of Death, and their record of one win and four draws on the road speaks volumes for their sturdiness away from home. Meanwhile, striker Robert Lewandowski has already registered five times against Mourinho's men this term and will, at the very least, give Pepe and Raphael Varane pause before joining any attacks.

Player to watch
Curiously, the greatest danger for Dortmund could come from a Gelsenkirchen native who failed to leave his mark on the first leg. Now aged 24, Mesut Ozil has been at Madrid since 2010, scoring 26 goals in 151 matches and making himself extremely popular with coach Mourinho – as well as team-mate Cristiano Ronaldo.

"Scoring isn't what's most important to me," says the expert passer, who enjoys an excellent understanding with Ronaldo and delivers more assists for the Portuguese forward than any other player. Ozil has quietly become indispensable for Madrid, forcing no less a player than Kaka onto the sidelines in the process.

The stat
3 – Madrid have recovered after losing a first leg by three goals or more on three occasions, first achieving the feat against European Champion Clubs' Cup opponents Derby County in 1975/76, when they triumphed 5-1 after a 4-1 initial loss. They then saw off Anderlecht 6-1 following a 3-0 reverse in the 1984/85 UEFA Cup, and overcame Borussia Mönchengladbach 4-0 after a 5-1 defeat in the same tournament the following year.

11 – Dortmund remain unbeaten in 11 Champions League games this term. Manchester United are the last club to have won the competition without losing a single match, having sealed the title without defeat in 2007/08.

What they said
"We can turn it around – it's very difficult, but we can do it. In football, anything is possible. On a crazy night when everyone performs at a high level, when every chance is a goal, we can turn it around," Jose Mourinho, Real Madrid coach.

"Towards the end of the game, at every corner Pepe was saying to me: 'You've already scored four goals – don't you think that's enough?' But nothing has been decided yet. We'll have to score again in Madrid," Robert Lewandowski, scorer of four goals for Dortmund in the first leg.

Barcelona-Bayern Munich

The match
Having suffered a catastrophic 4-0 loss in Germany, the mission for Barcelona will be to repeat their superb Round of 16 comeback against AC Milan, when they posted a 4-0 home victory in response to a 2-0 away reverse. That will mean injecting fresh energy into a side struggling to maintain its trademark fluidity, partly due to a string of injuries and suspensions in defence.

Indeed, the Catalan outfit displayed fragility at the back once again in Saturday's 2-2 draw at Athletic Bilbao, a game in which their final touch also let them down. Not for the first time, they were left in debt to Lionel Messi, who came on after an hour and struck an excellent goal – Barça's 100th this season – and contributed an assist in the space of ten minutes.

As for Bayern, they edged Freiburg 1-0 to rack up their 14th consecutive Bundesliga win and 27th in 31 outings, thus moving on to 84 points to set a new record in Germany's top flight. Belief is soaring in Jupp Heynckes' squad and, confident in their own ability and the scale of their advantage, they have left Barcelona needing a miracle to claw their way back.

Player to watch
Lionel Messi was almost a spectator during the first leg, attempting just one shot on goal, but the mercurial Argentinian looked to be finding his feet again during his half hour of action on Saturday. Just seven minutes after being sent on, he danced through the Bilbao defence and buried a low shot into the net with the inside of his left foot.

It was Messi at his best, echoing the impact he made when he came on to help seal a decisive 1-1 draw with Paris Saint-Germain in Barcelona's quarter-final decider. More than ever, the Blaugrana faithful have their fingers crossed, hoping for a stellar Messi display to dig them out of dire trouble.

The stat
– Barcelona have triumphed in their last ten home games against German clubs, winning three of them by four or more goals. They swept aside Bayer Leverkusen 7-1 in the last 16 in 2011/12, beat Stuttgart 4-0 at the same stage in 2009/10 and prevailed by the same scoreline in the 2008/09 quarter-finals against Wednesday's opponents Bayern.

9 – Bayern are hoping to reach their ninth showpiece in Europe's premier club competition and their third in the last four seasons. Only Madrid and Milan have graced more finals, contesting 12 and 11 respectively.

What they said
"There's no sense in talking about the end of a cycle. For me, the end of a cycle is when a club goes several years without winning anything. I think this club and our model deserves a lot of respect," Andres Iniesta, Barcelona midfielder.

"We need to keep our feet on the ground. I know we still face 90 very difficult minutes in Spain, and it will be important to stick to our tactical guidelines against Barcelona," Jupp Heynckes, Bayern coach.

Have your say
Can Real Madrid and Barcelona save themselves from elimination?