Celtic suffered a 4-3 Europa League defeat at Real Betis after an impressive opening half an hour had Ange Postecoglu's men two up in Seville.
A tricky first Group G fixture for the Bhoys initially went entirely to plan as Albian Ajeti broke the deadlock and Josip Juranovic's penalty doubled their lead.
But Betis' class told as Juan Miranda and Juanmi netted in quick succession before half-time, a feat the hosts repeated after the break.
Borja Iglesias and a second for Juanmi did the damage for Betis, with Anthony Ralston's late header not enough to ignite an unlikely Celtic fightback as a trip that promised so much ended in disappointment, although their sublime start suggested they could yet have a major part to play in a tough group.
Ajeti, signed by Manuel Pellegrini at West Ham, was influential against his former coach, turning in Jota's cross – the goal awarded after a lengthy VAR review, having initially been ruled out for handball – and then winning a penalty from Claudio Bravo, which Juranovic dispatched.
Joe Hart, who also played for Pellegrini and was replaced by Bravo at Manchester City, made two strong stops between those goals, but he was eventually beaten after 32 minutes.
Moments after a deflected drive struck the post, Miranda burst into the Celtic box to stab past Hart, and the visitors' lead was wiped out completely just 156 seconds later when Joaquin's delicate pass set Iglesias clear to square for Juanmi in front of an open goal.
Betis needed only five minutes of the second half to complete the turnaround, Iglesias meeting Sergio Canales' low left-wing cross with a smart flick.
Again, one goal followed another, with Juanmi controlling on his chest in the area following a corner and firing beyond the rooted Hart.
Tomas Rogic thundered against the foot of the post before Ralston nodded in David Turnbull's free-kick to set up a grandstand finish, but Betis held on.
What does it mean? Wait for away win in Spain goes on
Celtic headed to Seville without a host of first-team players, but they still had enough quality to threaten an upset. The Bhoys – facing Betis for the first time – were dreaming of a first away win against Spanish opposition in 19 attempts. In the city where they also lost the 2003 UEFA Cup final, however, reality soon intervened.
Ajeti looked like stealing the headlines after his early heroics, but it was Betis forward Iglesias who emerged the standout star. He stayed just onside to tee up Juanmi's equaliser and then finished superbly in the second half, contributing four shots and four chances created in total.
Harsh on Hart
Hart made four saves, including particularly impressive stops from Andres Guardado and Nabil Fekir at 1-0, but he still conceded four times. None of the blame could really be laid at the goalkeeper's door, though, and he looked the better of the two ex-City men, as Bravo also made four saves but gave away a penalty that could easily have proved costly.
Key Opta Facts
– Betis are unbeaten in all seven of their home Europa League group stage games (W4 D3). There were as many goals in this match as there were in their previous six such matches in the competition (F6 A1).
– Celtic remain winless in all 19 of their away games against Spanish opposition in European competition (D3 L16). However, this was the first time they have scored more than once in such a game since their first visit in September 1962 (2-4 vs Valencia).
– Just 156 seconds separated Betis' two first half goals, and just 142 seconds separated their two second-half goals in this match.
– Ajeti's opener for Celtic was his first in a major European competition, in what was his 11th appearance in either the Champions League (three) or Europa League (eight).
– Betis captain Joaquin (40y 57d) became the oldest outfield player to start a Europa League game since Francesco Totti for Roma against Villarreal in February 2017 (40y 149d).
Celtic go to Livingston on Sunday, with their next European fixture seeing Bayer Leverkusen visit at the end of the month. Betis go to Ferencvaros on matchday two, although their immediate attention is on Espanyol at home this weekend.