Wins over Sweden, Great Britain and Montenegro had seen Finland safely reach the knockout rounds with two matches to spare, though today's opponents Lithuania were always likely to pose a stiff test as the Wolfpack look to earn a more favourable tie in the Round of 16.
But the defeat means only a win against runaway group leaders and world champions Germany on Wednesday will see them climb a place into second, while a loss in their final group match sets up a tough Round of 16 match with Turkey or Serbia.
Finland were quick off the mark in front of their home crowd, racing into a 9-2 lead in the first two-and-a-half minutes. But back came Lithuania, and after Jonas Valanciunas of the Denver Nuggets scored the final four points of the quarter, the lead was back down to one, at 21-20.
Lithuania took that momentum into the second quarter, and ran with it. Eight points from Rokas Jokubaitis led the way as "the other Dream Team" shared the scoring around on the way to scoring 25 points to Finland's 15, taking a commanding 45-36 lead at half-time.
Defences were on top in the third quarter, as Finland managed to quell the Lithuanian attack but failed to put the required numbers on the board themselves, and only a three-pointer from Mikael Jantunen with a minute to go ensured they did not go further behind.
The Finns went for broke in the final quarter, as stars Lauri Markkanen and Miikka Muurinen finally showed the kind of form they have been showing this week in Tampere, continually chipping away at the Lithuanian lead that was 15 points with 07:16 to play.
However, they could not put together a dominant scoring run that really threatened their opponents, and a free throw from Arnas Velicka to put Lithuania five points clear with 13 seconds to go all but ended the contest, before a final two from Muurinen made the final score 81-78.
The win sees Lithuania join Germany and Finland in the last 16. For once, Markkanen was forced to share the top-scorer tag with Jantunen, as both finished on 19. Markkanen was also the joint-best rebounder in the game, level on 11 with Azuolas Tubelis.
Four Lithuanian players in double figures, headed by Jokubaitis on 16, was testament to how the winning side shared the scoring duties around. Jokubaitis went off injured, but still topped the assist charts for the game, with nine, three clear of the Utah Jazz's Markkanen.