Lionel Messi, Cristiano Ronaldo & Kylian Mbappe make UCL Best XI

After this week's Champions League quarterfinal first leg matches, here's ESPN FC's best XI.

Cristiano Ronaldo and Lionel Messi are joined by some very promising youngsters -- and a couple of veterans.

Do you agree? Have your say in the comments below.

Goalkeeper: Gianluigi Buffon (Juventus)

While Manuel Neuer starred in defeat for Bayern, only two keepers kept a clean sheet in this week's four matches, and Atletico Madrid's Jan Oblak was little more than a spectator as Leicester were dominated in their 1-0 defeat. In Juventus' 3-0 home victory, Buffon was kept rather busier against Barcelona and pulled off the save of the week when getting his fingertip to a Luis Suarez shot after a Lionel Messi pass. A vital away goal was kept at bay.

Centre-back: Nacho (Real Madrid)

In Munich, Real Madrid's defence had a makeshift look to it, with Nacho stepping in for the suspended Pepe and with Raphael Varane on the injured list. Alongside Sergio Ramos, the defensive utility man had to weather a storm, especially in the first half, but Bayern could only score a single goal through Arturo Vidal before Real prevailed 2-1.

Centre-back: Yohan Benalouane (Leicester City)

Leicester's rearguard had Atletico coach Diego Simeone claiming afterwards that England's champions were "betting everything on the second leg." A 1-0 deficit gives Leicester more than a sliver of hope. Benalouane, stepping in for captain Wes Morgan, made a series of important interventions. With Robert Huth suspended for the second leg and Morgan struggling to recover, the Tunisian reserve has become an important player for Craig Shakespeare.

Centre-back: Giorgio Chiellini (Juventus)

He could have conceded a penalty for a second half handball, but Juve's powerhouse reminded everyone the best exponents of central defending are still to be found in Serie A. His running battle with Suarez was a highly entertaining feature of Tuesday night. Leonardo Bonucci loses out to his partner for the crashing header that Chiellini delivered to put Juve 3-0 up and into a lead that should be unassailable.

Central midfield: Wilfred Ndidi (Leicester City)

A tough night for Shakespeare's men in Madrid, hard done by for the penalty awarded when Marc Albrighton fouled Antoine Griezmann outside the box. It was, though, an occasion of chasing shadows in red and white shirts. In that, Ndidi was tireless. The Nigerian is not N'Golo Kante, but least Leicester have a midfielder of similar energy output.

Central midfield: Saul Niguez (Atletico Madrid)

Atleti may rue being just that single goal ahead in their clash with Leicester, especially on the balance of play at the Vicente Calderon. Saul's quality in possession and cogent passing from his deep midfield role was a significant factor in Leicester's inferiority. He is an all-rounder who, at 22, looks more than worthy of the high price tag already against his name.

Attacking midfield: Christian Pulisic (Borussia Dortmund)

Forced to play barely 24 hours after escaping an attack on their team coach, Dortmund's players must be forgiven for not being at their best. They were 2-0 down, with Monaco also missing a penalty through Fabinho, but the introduction of the young American at half-time along with Nuri Sahin energised Thomas Tuchel's team. Pulisic carved great holes in Monaco with pace and creativity down the right flank, playing his part when Ousmane Dembele pegged it back to 2-1.

Attacking midfield: Lionel Messi (Barcelona)

Tuesday's 3-0 defeat to Juve may not have been a result to augment his supreme legacy but there was so much to enjoy in Messi's performance. Foraging deep in midfield as Barca's playmaker, Messi kept Juve's nerves on edge as he probed and prodded. Two passes, seemingly conjured from another planet, created chances that might have given Barca a vital away goal, but Andres Iniesta's miss and Buffon's superb save from Suarez's shot denied that.

Left forward: Paulo Dybala (Juventus)

The Argentinian is not quite an overnight sensation, since he cost Juventus €32 million from Palermo in 2015, but two goals against Barcelona were certainly a coming of age in a global sense. Two early strikes gave Juve the platform to hold off Barca in Turin. Dybala's speed, deadly finishing and finding of space forced a huge tactical rethink by Luis Enrique in abandoning his three-man defence. Though it came far too late.

Right forward: Cristiano Ronaldo (Real Madrid)

A century of European goals was reached and celebrated by the great man in scoring twice to push Real into that precious 2-1 lead in their tie with Bayern. It had been 197 days since he grabbed his last in Europe but following his 47th minute volley, the second -- a poacher's finish -- was only half an hour behind. And it was his sleight of foot that crucially saw Javi Martinez dismissed for two yellow cards.

Striker: Kylian Mbappe (Monaco)

When it comes to breakout stars of this Champions League season, surely Mbappe leads the list. Two goals against Borussia Dortmund further confirmed the 18-year-old Frenchman's burgeoning brilliance. His first goal was a little fortunate, coming off his thigh from an offside position, but his second was sublime, as he capitalised on an awful pass from Lukasz Pisczek and sped away to thrash home the ball. The sky appears to be the limit for him.