Xabi Alonso's emotional return to Anfield ended in defeat as Luis Diaz scored a hat-trick and Liverpool maintained their flawless Champions League record with victory over Bayer Leverkusen.

Alonso remains a hugely popular figure at Liverpool after winning the Champions League in 2005 and was heavily touted to succeed Jurgen Klopp this summer until he decided to stay in Germany.

Arne Slot was eventually appointed and his outstanding start continued as Liverpool once again recovered from a sluggish first half to overpower Leverkusen, who had controlled them comfortably before the break.

Luis Diaz broke the deadlock after 61 minutes with a deft lofted finish over keeper Lukas Hradecky from Curtis Jones' pass, Cody Gakpo adding the second two minutes later from Mohamed Salah's cross - the goal initially ruled out for offside before being given after a Video Assistant Referee review.

Diaz was on target again with a close-range finish seven minutes from time to give the scoreline an emphatic appearance that did not seem likely in the low-key, uneventful first period.

And there was still time for the Colombian to smash home a rebound to take home the matchball.

The win means Liverpool stay at the top of the new Champions League format standings with a maximum 12 points from four games.