Liverpool's Luis Diaz scored a hat-trick as they kept up their perfect Champions League campaign with a great second-half performance, beating Xabi Alonso's Bayer Leverkusen 4-0 at Anfield on Tuesday.

Arne Sloter's side are currently top of the Premier League table and leading the European club competition with four wins from four games. Only Aston Villa have a perfect record, and they're up against Club Brugge on Wednesday.

The Leverkusen defeat was a bit of a downer for Alonso, who's back as manager after previously playing for Liverpool. He lifted the Champions League trophy with the Reds in 2005 and was tipped to succeed former manager Jürgen Klopp, but that didn't work out.

"The result was probably more painful than the performance," Alonso told Amazon Prime. "But this is the Champions League, it's the highest level and today the performance wasn't enough for us.

"I tried to separate the pain of the game and the result from the good feeling of being back. "I'm really happy and grateful for the warm welcome from the Anfield fans," he added.

However, Sloter has shown he can hold his own as Klopp's replacement, notching up his 14th win in 16 games on Tuesday.

Diaz broke the deadlock in a pretty spectacular way in the 61st minute. He latching onto Curtis Jones's perfectly-placed pass, making his way through the Leverkusen defence and then lobbed the ball over goalkeeper Lukas Hradecky.

Two minutes later, Gakpo made it 2-0 with a diving header from a Mohamed Salah cross. The goal was initially ruled offside, but the decision was overturned by VAR.

Diaz got the second goal in the 83rd minute, meeting Salah's cross and holding off a challenge to fire the ball into the net past Hradecky.

"We have players all over the pitch, but actually I really enjoyed playing in this position today and I will work hard wherever I play on the pitch and I hope I can help the team," Diaz said, adding that he plans to go in search of the match ball.

He scored from close range in stoppage time after Darwin Nunez's shot was blocked, completing a hat trick and sealing victory for the six-time champions of Europe's top competition, who lost just once in all competitions last season.

"Four-nil, against a very good team, it's a good result, I don't know if it's the best result [of the season], but it's a good result," Gakpo told the media after the game.

Both teams were a bit lacking in quality during a pretty dull first half. Leverkusen's Jérémy Frimpong had a shot ruled out for handball just before half-time, while Gakpo dribbled past Hradecky on the left and missed a great chance for Liverpool.

Alonso's Leverkusen are currently 11th in the Champions League standings, with two wins, one draw and one loss. The match also gave last season's Bundesliga champions some valuable experience.

Alonso, who is 42, played 210 games for Liverpool between 2004 and 2009. He was involved in the amazing comeback against AC Milan in the Champions League final in Istanbul. After winning the Bundesliga title last season with an unbeaten record, there were rumours that Alonso would take over from Klopp as Liverpool head coach. However, in the end, Alonso stayed in Leverkusen.