The Standard Life GB men's team lost their opening pre-Olympic warm-up game in Houston 86-80 to Nigeria after a period of overtime.
The game was tied at 70 heading into the extra quarter, but Nigeria claimed victory, winning the high-scoring session 16-10.
Youngster Andrew Lawrence impressed by leading Great Britain with 19 points and, despite defeat, the Surrey-born guard was happy just to get more experience with the national side: "It was a tough game, we didn't execute on the fast break and in overtime they had the momentum, but all in all, it's a great experience for me and I hope to learn from this."
Eric Boateng supported Lawrence's stats with 13 points, hitting six of eight field goal attempts while Matthew Bryan-Amaning and Joel Freeland each had 10.
After a slow start from both sides, Nigeria had the upper hand, leading 17-16 after the first quarter, but GB responded and at the half tied the game at 36. Both teams were shooting well inside but were struggling from three-point range, missing a combined total of 13 long range attempts.
The third quarter saw Finch's team take a six-point lead going into the final quarter, 58-52, and looked to be punishing a tired looking Nigeria side who were carried by former NBA big man Ike Diogu who led all scorers with 33 points.
But, led by Diogu, the Nigerians hit back to tie the game at 70 to force overtime.
Standard Life GB head coach, Chris Finch commented on the defeat: "We will just go on from here really. Some games are good, some are bad, and there is still lots to work on. This was an evaluation of our guys to see who will and won't make the squad.
"We played the way we want to play and we should have won that game, we just needed to be smarter down the stretch and we got hurt on the rebounds. We have got to do better on that but these are first steps and the key is to get better from here."
Great Britain will play Lithuania in the early hours of Sunday morning in Houston before moving to San Antonio to play EuroBasket bronze-medallists Russia on Monday.
British Basketball has announced that BT Sport - the exclusive home of the NBA on UK television - will broadcast Great Britain's EuroBasket 2015 home qualifiers, in a deal agreed with British Basketball.
Despite being competitive for much of the game, Great Britain had to endure a second successive defeat to Latvia (68-76) at the University of Worcester Arena. Dan Clark scored 19 points and was backed up by Ashley Hamilton for 12.