Darmstadt are the first Bundesliga club to be relegated to the second division this season after a late 1-0 defeat at home to Heidenheim on Sunday.
Despite having three games left this season, Darmstadt can finish no higher than 17th in the table and can't avoid their fourth relegation from the Bundesliga.
"It's difficult. Right now I'm feeling empty inside. There were a few games that could have gone our way this season, but right now I don't know what to say," midfielder Fabian Nürnberger, visibly shaken, told broadcasters DAZN.
Darmstadt returned to the Bundesliga last year for the first time since 2016-17, but their comeback to the top tier was a disappointing campaign with 20 defeats and only three wins in 31 games so far.
Nikola Dovedan scored Heidenheim's winner in the 90th minute. With the win, Heidenheim, who were also promoted last year, have taken a crucial step in ensuring they will play in the Bundesliga next season.
Earlier on Sunday, relegation-threatened Cologne claimed a dramatic late 1-1 draw in a Bundesliga six-pointer at Mainz, while lowly sides Borussia Mönchengladbach and Union Berlin played out a goalless draw.
A goal from Leandro Barreira in the 29th put Mainz ahead after Karim Onisiwo made himself room for a shot, but his effort was pushed by Marvin Schwäbe, who couldn't do anything to stop Barrerio on the rebound.
Cologne had a huge chance to level the game early in the second half, but Luca Waldschmidt wasted the opportunity with a sloppy effort from the spot.
The guests, however, were awarded another penalty in stoppage-time and this was converted by Florian Kainz.
Both teams remain in the drop zone, Mainz in the play-off spot with Cologne right behind them. The result leaves Bochum outside of the relegation zone after they defeated Hoffenheim 3-2 on Friday.
In Gladbach, Union were the ones closer to a potential winner, with their best chance in the 25th minute when Kevin Volland hit the crossbar. They could have also scored 10 minutes later, but Brenden Aaronson's shot was nicely saved by Mortiz Nicolas.
Nicolas made a big save in the 51st to again deny Aaronson, this time from distance and after Gladbach gave the ball away in midfield with a sloppy pass.
Gladbach had a huge chance to score in the last minute, but Marvin Friedrich's header from a corner was saved by Frederik Ronnow.
Gladbach are 13th with four points separating them from the drop zone. Union are one position behind and two points above the danger.
"Of course we're disappointed that we weren't able to pick up three points at home against a direct rival. Overall, we lacked a bit of courage. We now need to discuss and address it during the week," coach Gerardo Seoane said.
Union coach Nenad Bjelica said his side had a "brave performance" and showed "a sign of life."
Volland added: "We can be satisfied with the second half. What we can't be so satisfied is with how we use our chances. If we become more efficient in that respect, we'd have probably picked up three points today."
