Best of 2017-18 Champions League knockout stage

Liverpool manager Jurgen Klopp (C) celebrates with midfielder Roberto Firmino (L) and striker Danny Ings following the UEFA Champions League semifinal second leg football match between AS Roma and Liverpool at the Olympic Stadium in Rome.

Liverpool's Roberto Firmino, center, challenges the Roma defense during the Champions League semifinal second leg soccer match between Roma and Liverpool at the Olympic Stadium in Rome.

Liverpool's Virgil van Dijk (C) reacts during the UEFA Champions League semifinal second leg soccer match between AS Roma and Liverpool FC at the Olimpico Stadium in Rome.

Real Madrid players celebrate at the end of their UEFA Champions League semifinal against Bayern Munich at the Santiago Bernabeu Stadium in Madrid.

Real Madrid's Karim Benzema celebrates after scoring his side's opening goal during the Champions League semifinal against Bayern Munich at the Santiago Bernabeu stadium in Madrid, Spain.

Bayern and Real Madrid players vie for the ball in the first leg of the semifinals.

Bayern's Thiago, left, and Real Madrid's Karim Benzema challenge for the ball during the first leg of the semifinals.

Real Madrid's Marco Asensio, top, celebrates after scoring his side's second goal in the semifinals.

Bayern's Joshua Kimmich, bottom, celebrates his side's opening goal with team mate James Rodriguez in the first leg of the semifinals.

Bayern's Corentin Tolisso, left, Real Madrid's Marcelo, center, and Bayern's Niklas Suele challenge for the ball during the semifinal first leg.

Bayern's Joshua Kimmich, left, celebrates his side's opening goal.

Liverpool's Roberto Firmino, right, celebrates after scoring his side's fourth goal in the first leg of the semifinals against Roma.

Liverpool coach Jurgen Klopp celebrates after Liverpool's Mohamed Salah scored the opening goal in the semifinals against Roma.

Liverpool's Sadio Mane celebrates after scoring his team's third goal in the first leg of the semifinals against Roma..

Liverpool supporters cheer ahead of the first leg of the semifinals against Roma.

Real Madrid's Cristiano Ronaldo converts a penalty to put his team through to the semifinals.

Referee Michael Oliver shows a red car to Juventus goalkeeper Gianluigi Buffon.

Bayern Munich players celebrate after the second leg against Sevilla.

Real Madrid's Cristiano Ronaldo is tackled by Juventus' Medhi Benatia during the second leg.

Juventus' Blaise Matuidi celebrates scoring his side's third goal in the second leg against Real Madrid.

Bayern's Javi Martinez, left, and Sevilla's Steven N'Zonzi challenge for the ball during the second leg.

Daniele de Rossi celebrates with teammate Alessandro Florenzi after Roma defeated Barcelona in the second leg of the quarterfinals.

Roma players celebrate reaching the semifinals.

Liverpool's Mohamed Salah scores his side's first goal in the second leg against Manchester City.

Manchester City's Leroy Sane in action during the quarterfinals second leg against Liverpool.

Liverpool's Roberto Firmino, second right, celebrates with his teammates after scoring his side's second goal.

Barcelona goalkeeper Marc-Andre ter Stegen, rear, as Roma's Patrik Schick, foreground right, tries to score.

Roma players celebrate with Kostas Manolas, second right, after he scored his side's third goal.

Barcelona's Lionel Messi reacts after missing a scoring chance during the second leg against Roma.

Pep Guardiola (L) manager of Manchester City reacts during the UEFA Champions League quarterfinal first leg match between Liverpool FC and Manchester City.

Liverpool midfielder Sadio Mane celebrates scoring during the UEFA Champions League first leg quarterfinal football match between Liverpool and Manchester City.

Liverpool's Alex Oxlade-Chamberlain celebrates after scoring during the UEFA Champions League quarterfinal first leg match between FC Liverpool and Manchester City.

Liverpool midfielder Mohamed Salah (C) celebrates with teammates after scoring the team's first goal during the UEFA Champions League first leg quarterfinal football match between Liverpool and Manchester City.

Liverpool's Mohamed Salah (R) scores during the UEFA Champions League quarterfinal first leg match between FC Liverpool and Manchester City.

FC Barcelona's Luis Suarez celebrates scoring a goal during the UEFA Champions League quarterfinal first leg match between FC Barcelona and AS Roma.

Barcelona's Gerard Pique celebrates after scoring during a Champions League quarterfinal first leg soccer match between FC Barcelona and Roma.

Roma striker Edin Dzeko (L) and midfielder Daniele De Rossi react during the UEFA Champions League quarterfinal first leg football match between Barcelona and AS Roma.

Roma defender Kostas Manolas (R) scores an own-goal beside Barcelona defender Samuel Umtiti (2L) during the UEFA Champions League quarterfinal first leg football match between FC Barcelona and AS Roma.

Real Madrid's Cristiano Ronaldo a goal on a bicycle kick against Juventus during a Champions League quarterfinal match at Allianz stadium in Turin, Italy. Real Madrid won the game, 3-0.

Real Madrid's Cristiano Ronaldo scores a bicycle-kick goal against Juventus.

Cristiano Ronaldo scores a bicycle-kick goal against Juventus.

Bayern Munich's Thiago scores a goal during a 2-1 Bayern win over Sevilla FC in a UEFA Champions League quarterfinal first leg game in Seville, Spain.

FC Barcelona's Lionel Messi celebrates a goal in his team's 3-0 win over Cheseal in the second leg of a Round of 16 Champions League at Nou Camp stadium in Barcelona, Spain.

Bayern's Sandro Wagner scores a goal against Besiktas during the second leg of a Round of 16 Champions League match in Istanbul, Turkey. Bayern Munich won the game, 3-1, and advanced on an 8-1 aggregate score.

Sevilla's Wissam Ben Yedder celebrates after scoring the opening goal of a 2-1 win over Manchester United in the second leg of a Round of 16 Champions League match at Old Trafford in Manchester.

Juventus goalkeeper Gianluigi Buffon celebrates his team's come-from-behind 2-1 victory over Tottenham in the UEFA Champions League.

Juventus goalkeeper Gianluigi Buffon clears the ball during the UEFA Champions League Round of 16 match against Tottenham at Wembley Stadium in London. Juventus won the match, 2-1, to advance.

Real Madrid Keylor Navas grabs the ball in the second leg against PSG.

Real Madrid's Karim Benzema shoots in the second leg against PSG.

Real Madrid's Sergio Ramos jumps in the arms of Lucas Vazquez as they celebrate the opening goal in the second leg against PSG.

Liverpool's Roberto Firmino, left, vies for the ball with Porto's Felipe.

Manchester United goalkeeper David De Gea punches the ball away from Sevilla's Clement Lenglet during the UEFA Champions League Round of 16 first leg match at the Ramon Sanchez Pizjuan stadium in Sevilla. Thanks to De Gea's efforts, Man U held Sevilla to a 0-0 draw.

Thomas Mueller celebrates after one of his two goals in Bayern Munich's 5-0 win over Besiktas in UEFA Champions League Round of 16 play.

Barcelona's Lionel Messi celebrates scoring a goal in a 1-1 draw vs. Chelsea at Stamford Bridge stadium in London.

Real Madrid's Cristiano Ronaldo celebrates after scoring a goal against PSG in Champions League play.

Real Madrid's Cristiano Ronaldo (left) vies with Paris Saint-Germain's goalkeeper Alphonse Areola during the UEFA Champions League Round of 16 first leg match at the Santiago Bernabeu stadium in Madrid. Real Madrid won the game, 3-1.

Porto's Hector Herrera collides with Liverpool's Trent Alexander-Arnold during the UEFA Champions League Round of 16 first-leg match at the Dragao stadium in Porto, Portugal. Liverpool won the game, 5-0.

Manchester City's Sergio Aguero, celebrates his team's third goal in a 4-0 win over FC Basel during UEFA Champions League Round of 16 action in the St. Jakob-Park stadium in Basel, Switzerland.

Basel's Valentin Stocker and Manchester City's Nicolas Otamendi jump over Manchester City's goalkeeper Ederson Moraes during UEFA Champions League play at the St. Jakob-Park stadium in Basel, Switzerland. Man City won the game, 4-0.

Manchester City's Kyle Walker (right) vies for the ball with Basel's Mohamed Elyounoussi during the UEFA Champions League Round of 16 first leg match at the Saint Jakob-Park Stadium in Basel.

Tottenham Hotspur's Harry Kane applauds supporters after a 1-1 draw against Juventus in Turin, Italy, in UEFA Champions League play.

Juventus' Alex Sandro (center) gets sandwiches between two Tottenham Hotspur players during UEFA Champions League play at the Allianz Stadium in Turin, Italy. The game ended in a 2-2 draw.