Darius Hargrove scored the winning basket with one second left in overtime to give CSU Asesoft Ploiesti a thrilling 97-95 win over BC Donetsk.
CSU were led by Arvydas Cepulis' 29 points, Hargrove's 26 and Catalin Burlacu's 20 as they held off the determined Ukrainian club.
This was a wild game that saw both teams go on extended scoring runs before a fourth quarter and overtime in which the lead went back and forth.
Donetsk led 27-19 early in the second quarter only to see CSU turn the game around with a 16-0 run to go on top, 35-27.
The Romanians opened the second half with 10 straight points and eventually pushed their lead to 16 before Donetsk mounted a comeback of their own, going on a 16-2 run to pull within two near the end of the third quarter.
The teams exchanged leads 12 times throughout the fourth quarter and overtime before Hargrove's last-second jump shot ended it.
Marque Perry led Donetsk with 33 points, including 17 of 18 at the free throw line.
Rostyslav Kryvych added 19, hitting four of eight from three-point territory.
Although neither team will advance to the Last 16, both showed their quality in this hotly-contested finale.
The loss capped a disappointing European season for Donetsk, who had an eight-point first-leg lead in their Eurocup Qualifying Round tie with Bilbao, only to fall by 11 in Spain and fail to advance.
In the EuroChallenge, the Ukrainian outfit continued to struggle, with coach Ramunas Butautas eventually getting fired.
The club replaced him with Drazen Anzulovic, who will now attempt to bring success on the domestic front.
Ploiesti will also have to be content with focusing on matters in their own top flight in Romania.
Drazen Anzulovic, BC Donetsk head coach:
"It was a very balanced game, we had an 8 point lead and then Asesoft had 16 consecutive points. Our defense didn't do a good job today, but this was only my third game as a coach of this team and my main objective is to improve the defense.
"We had three key players injured, so we didn't have the opportunity to do our usual game. I know that at the start of this competition we were considered the team with the best chances to qualify, but on the court the thing were different. We are satisfied with the experience in playing in the Eurochallenge and we hope that next year we will manage to reach our goal. Now, we have to focus on the national championship."
Joshua Asselin, player BC Donetsk:
"We are very sorry for this loss and for the losing the qualification, but we had many things to learn from this experience."
Arvydas Cepulis, player CSU Asesoft:
"Finally we managed to win a balanced game! After so many matches lost in the last second we are happy that it was our turn to be happy at the end. It's good for us. I don't know if this was my best game this season, but my colleagues gave me the ball and so I had the opportunity to shoot more.
We have a long championship in front of us; it's too early to think about a new European season."
Vladimir Arnautovic, CSU Asesoft head coach:
"The win against Donetsk is very good for the mental of my players. Now, they are happy after we lost two games in the last second. If we had won at least one of these games, now we would have been qualified. But for us, playing in such powerful competition is very good because we can't accumulate this kind of experience in our championship.
"I'm very happy for the win, especially because Carutasu and Griffith were injured and they couldn't play at their maximum capacity and we couldn't count on Ilic, because he suffered a sprain three days before the game.
Now, we will focus on the national championship, because we want to be back in this competition next year and maybe then we will be luckier. "