Union Berlin missed a chance at reinstating their four-point lead at the top of the Bundesliga, going down 2-1 at bottom side Bochum on Sunday.
Union came into the weekend with a four-point lead, but the gap was cut to just one after Bayern Munich defeated Hoffenheim 2-0 on Saturday.
Union coach Urs Fischer admitted that "Bochum were simply better".
"We didn't have the right answers," he told AFP subsidiary SID.
Bochum coach Thomas Letsch said: "I recognised how much desire the team had to get something out of the game (from the start).
"We played a great game and deserved to win."
Bochum took the lead in the final minute of the first half when Philipp Hofmann headed in a corner.
Looking to ignite a tired-looking side exhausted by frequent midweek matches as a result of their Europa League campaign, Fischer made three changes in the 63rd minute.
However it was the home side which continued to look fresher, scoring a second on the counter in the 71st minute when Christopher Antwi-Adjei crossed for Gerrit Holtmann to score.
Union had a chance to mount a comeback when awarded a penalty in the 77th minute, but Bochum goalkeeper Manuel Riemann saved Milos Pantovic's tentative spot-kick.
Pantovic got on the board in the last minute of injury time, but it was not enough as Union failed to secure three points for just the fourth time this season.
Union midfielder Rani Khedira said his side only had themselves to blame for an "unnecessary and frustrating" defeat.
"The first Bochum goal we practically scored ourselves, the second we invited them for a counter.
"If we don't do the basics, it's going to get difficult. We need to push ourselves to the limit in every game."
HERTHA TOAST 'DIRTY VICTORY'
The win saw Bochum leapfrog Schalke, who finished the weekend stranded in last place after going down 2-1 at Hertha Berlin in Sunday's late game.
The visitors, who fired coach Frank Kramer after their midweek German Cup exit, started furiously and had two goals chalked off for offside in the opening 20 minutes – both scored by former Union Berlin player Marius Buelter.
Hertha took the lead in the 48th minute when French midfielder Lucas Tousart's swerving shot squirmed under the dive of Schalke keeper Alexander Schwolow.
Schalke looked like they had snared a late point when another Frenchman, midfielder Florent Mollet, skidded a shot through the legs of Hertha defender Agustin Rogel to make it 1-1 with five minutes remaining.
Hertha re-took the lead just three minutes later when Ivorian striker Wilfried Kanga raced onto a pass 40 metres from goal and evaded the Schalke defence to give his side just their second win of the season – and their first at home.
After the game, Hertha coach Sandro Schwarz toasted his side's "dirty victory", saying he was "incredibly happy" with his side's performance.
"We showed outstanding spirit at the back... It was very emotional. We all needed that."
Interim Schalke coach Matthias Kreutzer said although his team "were heading home again without the three points, we showed that the distance isn't so big."