A lack of consistency has proved costly for the team coached by Robin Dutt, who was tasked with breathing new life into the club after the departure of long-time coach Thomas Schaaf last season.
However, a crucial 2-1 victory last week against Hanover 96 lifted Werder to 32 points, eight above the relegation zone, and a win over Schalke should see them secure safety with five games remaining but sporting director Thomas Eichin remains wary.
“We have not reached the other side of the river,” Eichin told reporters. “We should not be allowed to believe we are already somewhere.”
Dutt will have to reshuffle his team for the encounter with top scorer Aaron Hunt ruled out with a thigh muscle injury.
Hunt had some more bad news for the club a few days ago when he announced he would be leaving at the end of the season.
“We are only playing against teams above us in the table, including Schalke and Bayer Leverkusen, and against (champions) Bayern Munich,” Werder keeper Raphael Wolf said.
“We should not feel that we are safe. We did not go into the season to get 32 points and then stop playing football.”
Werder have their work cut out against Schalke, who are chasing a Champions League berth having lost just one of their last 13 league games.
Improving Schalke have climbed up to third on 54 points, one behind Borussia Dortmund, who entertain VfL Wolfsburg.
“If we continue playing as we have done then I think we will have that Champions League spot in the end,” said teenage Schalke midfielder Max Meyer, who has had a stellar campaign.
“It would obviously be nice to be standing above Dortmund in the end.”
After losing 3-0 to Real Madrid in their Champions League quarter-final first leg on Wednesday, Dortmund will be looking to return to form on home soil and retain the edge over Ruhr valley rivals Schalke with a win over the in-form Wolfsburg.
Bayern Munich, who have already secured the title, travel to Augsburg.
(Editing by John O’Brien)