GB's Luol Deng led all scorers with 26 points, Joel Freeland had 25, while Calderon led Spain with 19 points.
"Same old story," said Freeland after GB came up short for the second game running. "This time we were a lot more mature, we were fighting right towards the end and we hit some really important shots.
"We played great, held our nerve and hit some clutch shots. We were always in it, it was a great game, we have just got to keep doing what we are doing. We are fighting."
He added: "I'm proud to say we played in that game and that we did everything we could."
Spain came out shooting from the off and quickly built a 6-0 lead, but Great Britain kept in touch thanks to Freeland who scored GB's first 8 points of the game.
After a Deng three-pointer cut the GB deficit to 14-11, Spain scored eight unanswered points and posted a 24-15 lead at the end of the first quarter.
A strong start for Great Britain in the second cut the deficit to 25-20, but once again Spain replied with back-to-back three-pointers and they held on to lead 37-29 at the half.
Spain pushed the lead to 60-48 by the end of the third and looked good for the win before GB began their comeback in the final quarter.
Down 64-52, Deng took over the GB scoring, hitting eight of the next 10 GB points and cutting the deficit to 68-65. After Spain increased their lead to six, back-to-back baskets from Freeland made it 71-69.
After Spain missed on their next possession, Great Britain had a chance to tie the game with less than a minute remaining but they turned the ball over on two straight possessions. Spain then looked to have wrapped the game up as Calderon made a number of free throws, but three-pointers from Dan Clark, Nate Reinking and Deng set up the dramatic finale.
"It was nice to see us make shots and play with confidence," commented GB head coach Chris Finch. "It was important to hang in there even when the gap was ten points.
"We had some phenomenal efforts from some of our role players when Pops and Luol got into foul trouble. They stepped up and couldn't have picked a better moment.
"We had a chance to win in the end."
Elsewhere in Great Britain's group, Russia edged Brazil 75-74 and Australia enjoyed an 81-61 victory over China.
The GB Men are back in action on Saturday evening when they take on Australia (8pm) in a game they must win to have any hopes of qualifying from the group.
