In-form Bayer Leverkusen midfielder Florian Wirtz enjoyed a dream Champions League debut Thursday, as two first-half goals powered the Bundesliga winners to a 4-0 humiliation of Dutch side Feyenoord.

Xabi Alonso's men killed the game off by half-time, their attacking pace and precision overwhelming a defensively frail Feyenoord, who looked a shadow of last season's side under Arne Slot, now at Liverpool.

"Obviously we could all see how bad we were. You can't give away the ball like we did in the Champions League," said Feyenoord's In-beom Hwang, who was making his debut.

"I'm just sorry to the fans who came to the stadium to support us. In the coming games, we will be better," added the South Korean midfielder.

The match started terribly for the hosts, Algerian defender Ramiz Zerrouki losing possession in front of goal with just five minutes gone, gifting the ball to midfielder Robert Andrich.

A simple pass set up Wirtz for a one-on-one with Timon Wellenreuther in the Feyenoord goal and the German made no mistake, slotting the ball into the bottom-left corner with confidence.

Wirtz is in red-hot form, already finding the back of the net three times in the Bundesliga this season and also scoring on international duty for Germany.

Despite playing more than 150 times for Leverkusen, injury had kept him out of Champions League action, meaning the Feyenoord clash was his debut at Europe's top level.

Zerrouki thought he had redeemed himself just three minutes later after he bundled home from a scrappy corner, but the goal was chalked off for offside.

When the Bundesliga side doubled their advantage after 30 minutes, it was hardly against the run of play but came with a large slice of luck.

- 'A tough match' -

A miskick from Nigerian international striker Victor Boniface fooled the entire Feyenoord defence and set Dutchman Jeremie Frimpong clear down the right.

Frimpong squared the ball to Spanish international Alejandro Grimaldo for a tap-in.

But there was nothing lucky about Leverkusen's third and Wirtz's second, as Feyenoord leaky defence was again exposed on the break.

A sweeping move down the right left Frimpong a free cross and his pinpoint ball found Wirtz completely unmarked in the Feyenoord box, picking his spot past Wellenreuther.

The first-half rout was completed on the stroke of half-time as an innocuous seeming header from Burkina Faso defender Edmond Tapsoba somehow squeezed through Wellenreuther's legs, officials ruling it an own goal.

The De Kuip stadium faithful made their displeasure known at the half-time whistle, boos ringing around a ground that had been buzzing with anticipation 45 minutes earlier.

"We knew before it was going to be a tough match against the German champions, a great team. But we never thought we would be 4-0 down at half-time," said defender Thomas Bellen.

With the match already over as a contest after the first-half fireworks, the second half seemed pedestrian in comparison.

Feyenoord pressed gamely and came close to a consolation goal a couple of times but the German defence held firm for an impressive start to their European campaign.

Leverkusen host AC Milan On October 1 in the next round of the new-look Champions League, while Feyenoord travel to Girona on October 2.