PSV Eindhoven slipped to their first UEFA Europa League defeat of the season as Marcell Jansen's penalty gave Hamburger SV the edge after the first leg of their round of 32 tie.
Jansen struck from the spot on 26 minutes after Mladen Petrić had been felled to hand PSV only their second reverse of the campaign in all competitions, and ensure Hamburg newcomer Ruud van Nistelrooy a happy renewal of acquaintances with his former club.
Van Nistelrooy was made to wait before facing PSV for the first time since leaving in 2001 and, sitting on the bench, the Dutch international saw the visitors begin positively. Indeed, the Eredivisie leaders would have forged ahead but for a flying Frank Rost save from Orlando Engelaar's flicked header.
That sparked a slumbering Hamburg into action, a slick exchange of passes allowing Petrić to burst into the box. Stanislav Manolev's ill-timed challenge upended the Croatian international, and Jansen calmly dispatched the spot-kick. Even the half-time break did little to halt Hamburg's momentum, with Andreas Isaksson forced to deny Petrić and David Rozehnal in quick succession after the restart.
Backed by a vocal travelling support, PSV responded with intent, and Rost was a spectator when Danko Lazović sent a shot spinning narrowly wide before Ola Toivonen wastefully fired over.
The Hamburg fans had to wait 64 minutes before getting the chance to see Van Nistelrooy, and the penalty-box prowess that came to the fore at PSV was immediately evident. He cleverly rolled Francisco Rodríguez and would have given Isaksson a more strenuous test had he been able to connect cleanly with his shot.
Balázs Dzsudzsák's directness down the left threatened to open up Hamburg in the latter stages, but neither Toivonen nor Otman Bakkal could take advantage of the Hungarian's high-quality service to even things up ahead of next Thursday's second leg.