A promising Celtic start was undone by a string of defensive lapses as Bayer Leverkusen ruthlessly punished their hosts to take victory in their Europa League meeting in Glasgow.

A frantic game played in front of an, at times, raucous crowd raged in the opening minutes, before Piero Hincapie finished after David Turnbull's slip.

Florian Wirtz chipped the ball over Joe Hart to make it 2-0, Lucas Hilario's penalty killed Celtic's second-half momentum before substitute Amine Adli smashed in a fourth with the last kick.

Defeat leaves Celtic bottom of Group G with zero points with a double header against also winless Ferencvaros to come next, while Leverkusen, whose fourth was just reward for a glut of late surges, have a 100% record alongside Real Betis.

The surprise returns of Kyogo Furuhashi and captain Callum McGregor to the Celtic XI after injuries sent an electricity around Celtic Park pre-match, as the fans sensed their chances of victory amid a poor run of form were suddenly revived.

Their optimism initially proved well-judged as - after surviving an offside goal for Wirtz inside one minute - they played with pace and vigour, only to be undone by defensive mistakes and inspired Luka Hradecky in the Leverkusen goal.

Kyogo in particular was outstanding as his movement reinvigorated a recently stunted Celtic.

The Japanese forward was first denied by a stunning covering tackle from Jonathan Tah, while Hradecky saved his efforts either side of the break.

Jota was also lively, and was himself prevented spectacularly by Hradecky as Ange Postecoglou's side desperately attempted to avoid a fifth defeat in eight games.

But as has been the theme of Celtic's season, slackness cost them dearly against a quality Leverkusen side with just one defeat this season - a 4-3 loss to Borussia Dortmund.

First, Turnbull slipped after feinting to play the ball out in his own box, and that allowed Mitchel Bakker to square for Hincapie to sweep home the opener on 25 minutes.

A lack of communication at the back then allowed 18-year-old Wirtz to sneak in behind and remain onside before lifting the ball into the top corner for his sixth goal in seven games.

That left Celtic chasing the second half, and despite another promising spell, Hradecky and Leverkusen's attacking quality halted their challenge.

Former Celtic right-back Jeremie Frimpong twisted and turned before forcing Hart into a save, and Cameron Carter-Vickers was judged to have blocked the follow up with his hand.

Hilario calmly sent Hart the wrong way from the penalty spot to effectively end Celtic's hopes of victory with half an hour to play.

By this point Leverkusen were content to soak up Celtic's weary attacks and punch on the break with their searing pace.

And Adli finally took one of their late chances as he sent a rocket beyond Hart on the angle to finish a fine night for the visitors in style.

Man of the match - Lukas Hradecky

What did we learn?

Leverkusen are a quality side who taught Celtic a lesson. The home side's attacking approach put them on the back foot early on, but they weathered that storm, and imposed themselves on the match.

Wirtz looks like a star of the future, and his goal - a fine finish after Leverkusen pounced on a slack pass and surged forward - demonstrated his and his side's prowess and they had plenty of further chances.

They were able to switch to a back five late on and use their pace to devastating effect as Celtic continued to plug away to no avail. It demonstrated their ability to adapt, while Celtic seem incapable of playing different ways.

Such a high tempo approach from Celtic is a thrill to watch when Kyogo and McGregor are in the team, but question marks remain about the mobility of Rogic and Turnbull in this system. When Celtic lose the ball, the pair are often caught too far up the pitch.

Yes, Postecoglou's side had chances (18 shots), but they've conceded eight in two games in the Europa League so far. The reality is with the current personnel, they need to take nearly every chance that comes their way at this level to win matches, because they cannot keep the ball out at the other end.

Whether by tactical changes, coaching, or recruitment in January, Celtic need to improve without the ball. If they can do that, they have the potential to be an effective side.
What the stats say

None of Bayer Leverkusen's last 21 matches in European competition has been drawn, with the German side winning 13 and losing eight.
Celtic failed to score for the first time in 20 matches in European competition (incl. qualifiers), since a 2-0 Europa League defeat at CFR Cluj in December 2019.
German sides have won six of their last seven European away games against Scottish sides (L1), with Leverkusen winning the last two against Rangers and Celtic respectively. Indeed, Celtic have been responsible for four of those defeats, losing to a different club each time.
Celtic have conceded 2+ goals in each of their last nine Europa League games. Since the competition was rebranded in 2009, only Slovan Bratislava have had a longer such run in the competition (11 games between 2011 and 2019).
With Florian Wirtz (18y 150d) and Piero Hincapié (19y 264d) finding the net, tonight was the first time Bayer Leverkusen have had two teenagers score for them in the same major European game.