Great Britain improved again in their first game of the Marca tournament in Seville, but predictably came up short to lose 84-63 to world champions Spain.
Although Spain were missing Pau Gasol, an NBA champion with the LA Lakers this season, they still had too much strength in depth for GB.
Nate Reinking and Nick George hit 11 points each for GB and Mike Lenzly again impressed with 10 points.
GB will play Olympic semi-finalists Lithuania in their second game.
After last weekend's problems with missing players, GB welcomed back Andrew Betts and Robert Archibald.
Coach Chris Finch pointedly started Flinder Boyd, Joel Freeland, George, Dan Clark and Lenzly - his five best players from last weekend - and his faith was rewarded with an opening 8-4 lead.
But Spain are a side good enough not just to punish opponents' mistakes, but also their audacity, and proved that as Mark Gasol hit five points Jorge Garbajosa six as they closed out the quarter with a 19-6 run.
In the second quarter, new NBA draftee Ricky Rubio twice combined with Juan Carlos Navarro for three-pointers as the lead stretched to 32-17.
But GB responded with threes from Boyd and Nate Reinking (2) to trail just 44-32 at half-time.
Worryingly, starting point guard Flinder Boyd limped out of the game with 4:52 remaining in the third quarter after turning an ankle.
Despite that setback, GB enjoyed a solid third quarter with Kieron Achara topping off some strong work on the boards with a three and Lenzly hitting another.
Finch put in all six of his remaining players in the final quarter and will have been gratified that the lead only extended beyond 20 points in the last two minutes, when Spain scored four free throws awarded for a Joel Freeland technical foul.
But with Spain one of GB's opponents in EuroBasket Group C in Warsaw next month - the so-called Group of Death - the size of his team's task will certainly not have escaped him.
Navarro and Gasol led Spain's scorers with 17 points apiece and Rubio added 13.
Despite the defeat, Finch was pleased that Reinking was able to rediscover his shooting tough after a disappointing weekend at the O2
"That was good," he said afterwards. "He was trying to do too much so we just told him, 'get open where we can find you.
"Although Spain are not the most physically imposing team here they just play so fast and they have all the pieces."