Great Britain's men lost their latest EuroBasket 2015 qualifier to Bosnia 80-67 at the Copper Box in London.
It was a second defeat by 13 points in as many matches for the side, who lost 83-70 to Iceland on Sunday.
Bosnia's lead was cut from 23 points to seven inside the final quarter, but the hosts were unable to get ahead.
Dan Clark top scored for GB with 14 points and nine rebounds, while Brooklyn Nets' Mirza Teletovic was Bosnia's leading scorer with 25 points.
It was GB's first home defeat in a qualifying game since 2006, ending a 10-game winning streak.
GB's squad is without NBA players Luol Deng and Joel Freeland, both of whom opted to sit out this summer's programme.
"We were playing catch-up for most of the game," said Clark.
"We only really found some rhythm in our game in the second half.
"In the end, it was too little too late - we've got to execute better and concentrate for the whole 40 minutes."
Trailing 67-44 late in the third quarter, GB hit a 22-6 run, with Clark and Kieron Achara both featuring heavily, to trail 66-73 with 3:55 left to play.
Bosnia then showed their top-flight experience to score seven of the next eight points to close out the game as GB missed opportunities to take an unlikely victory.
GB need to win their two remaining games to have a realistic chance of making a fourth successive EuroBasket finals appearance possible.
Only the top team in the three-nation group is guaranteed a place in next year's European Championship. Great Britain's next match is against Iceland at the Copper Box next Wednesday.