UEFA.com looks at the portents for the second legs, including a worrying record in Germany for Real Madrid CF and Chelsea FC's semi-final toils against Spanish sides.
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FC Bayern München (0) v Real Madrid CF (1)
• Bayern's home record against Madrid is W8 D1 L0. While Bayern's home record versus Spanish clubs reads W15 D5 L1, Madrid have won only twice in 27 trips to Germany, most recently 6-1 at FC Schalke 04 in this season's round of 16. The Liga team have suffered five losses in their last 23 European away fixtures – four of them in Germany.
• Bayern have recovered from an away first-leg reverse to win the tie on nine occasions; they have suffered ten defeats, including seven in the last nine contests. The Munich club have won five of six ties after losing 1-0 away first, most recently against FC Basel 1893 in the 2011/12 round of 16 when they prevailed 7-0 in Munich – the biggest UEFA Champions League knockout victory. The exception came in the 1989/90 European Cup semi-finals, AC Milan going down 2-1 in Munich but triumphing on away goals.
• Madrid have gone through in 43 of 56 European ties after success in the first leg at home, including against Borussia Dortmund in this season's quarter-finals. When winning 1-0 at the Santiago Bernabéu first time out they have progressed in four of six ties, both defeats coming against Juventus, in 2004/05 and 1995/96; on each occasion they lost the second leg 2-0.
Chelsea FC (0) v Club Atlético de Madrid (0)
• In UEFA competition, Chelsea have lost the tie twice on the seven occasions they have drawn their first leg away from home, defeating Galatasaray AŞ in this season's round of 16 (1-1 away, 2-0 home). When drawing 0-0 away first they have won one tie but lost two, most recently against FC Barcelona in the 2008/09 semi-finals (0-0 away, 1-1 home).
• Chelsea have won only one of their four previous UEFA competition semi-finals against Spanish opponents, against Barcelona in the 2011/12 UEFA Champions League. They lost to the same opponents in that competition in 2009 and, in the UEFA Cup Winners' Cup, against RCD Mallorca (1998/99) and Real Zaragoza (1994/95).
• Atlético, who have advanced through both UEFA competition ties in which the home first leg finished 0-0, have won only once in nine away fixtures against English sides, losing four and drawing four. Their sole success was a 2-0 victory at Leicester City FC in the 1997/98 UEFA Cup first round. In seven two-legged ties with English clubs in UEFA competition, Atlético have won five and lost two.