Coach Thorsten Fink has seen his team slump to three straight defeats, including an embarrassing 9-2 demolition by newly-crowned champions Bayern Munich.
The defeats have put some distance between Hamburg and the Europa League spots they have been chasing all season and have triggered a furious reaction from Fink.
"There are no more excuses," Fink told reporters after a long talk with his players on Wednesday. "Everyone has to see how they can improve."
"I think he can handle this role better at the moment," said Fink, piling further pressure on the Dutchman, who has yet to shine after his return to Hamburg this season.
Fink also promised changes in the summer and those changes would be determined by each of his players' commitment starting Saturday.
"What I now want to see is who will bleed for the club, who will give it everything they have for the club and its people, the people who work here.
"Those who will keep working will stay on in the summer. The others can start looking for a new club."
"I have thought long about it and if we do not change some things now then we will not move forward," said Fink. "We are going to Mainz to get that good result."
With the Bundesliga title already secured, leaders Bayern Munich could be forgiven for taking their foot off the pedal after also clinching a Champions League semi-final spot on Wednesday with a 4-0 aggregate win over Italy's Juventus.
With their treble season still on track, coach Jupp Heynckes is expected to rest several key players when they host Nuremberg in their Bavarian derby, Bayern's first home appearance as the new league champions.
Dortmund, who won last season's title, have also moved into the Champions League last four but are eager to tighten their hold on second place on their trip to bottom-placed Greuther Furth.
