Southampton’s unbeaten pre-season came to an end at the final hurdle as slick La Liga opponents Athletic Club ran out 3-1 winners at St Mary’s.
The visitors, last season’s Copa del Rey finalists, scored twice in 10 minutes late in the first half through Mikel Vesga and Asier Villalibre.
Half-time substitutes Tino Livramento and Theo Walcott combined for the latter to reduce the deficit within a minute of coming on – the first of a few promising contributions from 18-year-old debutant Livramento.
But Saints were caught on the counter just as they were enjoying their best spell, as fleet-footed winger Nico Williams teased Jan Bednarek with a cross the defender could only put through his own net to complete the scoring on the hour.
This was always likely to be Saints’ stiffest test of the summer, but the hosts settled to their task as Yan Valery careered down the right and crossed low, but Michael Obafemi was just unable to apply the final touch.
Valery then showed his defensive nous to shut down Iker Muniain, a Spanish international winger of some repute, as the Frenchman staked his own claim in response to the arrival of Livramento as competition for Kyle Walker-Peters.
Athletic Club argued they should have been awarded a penalty when Ibrahima Diallo challenged Oier Zarraga from behind, but referee John Busby adjudged no contact was made.
Saints have made a happy habit of keeping their opponents at bay throughout pre-season, but it was from a simple set-piece that the visitors edged in front on 33 minutes.
Skipper Muniain whipped in a corner from the right that curled away from Alex McCarthy and on to the head of Vesga, whose downward header nestled just inside the far post.
Athletic pushed on and threatened again from another corner, this time taken short and eventually delivered by Zarraga to the far post where Villalibre was lurking, whose backheel was blazed over by strike partner Raúl García.
The Basque club did get their second just before the interval when Williams dispossessed Stuart Armstrong and ran at the Saints defence, timing his pass just right for Villalibre, who emphatically rifled the ball in off the underside of the crossbar.
Saints responded with a positive run down the left from Moussa Djenepo, which carried the winger into the box and invited a challenge from Williams, who seemed to impede him from behind without punishment.
A double substitution at the break gave Saints a fresh look and fresh impetus, with debutant Livramento replacing Romain Perraud, prompting Djenepo to move to left-back, and Walcott replacing Ibrahima Diallo, leaving Armstrong to partner Oriol Romeu in midfield and Walcott and Valery as the wide men.
The reshuffle paid instant dividends. Livramento, with his first touches in red and white, broke forward and lofted a pass over the top for Walcott, who took it in his stride and stretched to prod the ball through the legs of newly-introduced goalkeeper Jokin Ezkieta within 60 seconds of the restart.
There was a new lease of life about Saints, as the energetic Valery won a free-kick right on the edge of the box, albeit not in a shooting position, before Bednarek angled a shot wide of the far post from another set-piece.
Then Livramento created another chance with a clever ball seeking out Obafemi, but Ezkieta was out sharply to leave the youngster with little to aim at.
Saints’ growing momentum was punctured on the counter-attack by the dangerous Williams, who set off down the right and produced a cross that left Bednarek in a hopeless situation, as the defender inadvertently turned the ball into his own net at the near post.
The new-look right side of Livramento and Valery continued to pose problems, and the two combined to good effect when the former cut the ball back and the latter drove a low shot just beyond the far post.
A raft of changes for the visitors in the 74th minute served to kill the rhythm of an entertaining second half, as Saints tasted defeat for the first time since the final day of the Premier League campaign.