Schalke were beaten 3-1 at home by arch-rivals Borussia Dortmund last Sunday, leaving them without a point at the bottom of the league after four straight defeats, and Magath has admitted his squad is lacking confidence.
The Royal Blues face Freiburg in the Bundesliga on Wednesday, then Borussia Mönchengladbach on Saturday before taking on Benfica on September 29 in the
Champions League, and badly need a moral-boosting win.
Despite signing Spain veteran Raul and Holland's Klaas-Jan Huntelaar, Schalke are struggling for form and have lost their last five games including the 1-0 defeat at Lyon in the Champions League.
Magath is both team manager and trainer at Schalke and has previously won the German league title with both Bayern Munich and Wolfsburg.
He is coming under increasing pressure in his second season at the Gelsenkirchen club, but has Tönnies's backing.
"I do not doubt the quality of the coach," Tönnies, the chairman of Schalke's board, told news agency SID.
Magath has made sweeping changes at Schalke, but Tönnies insists the new team needs time to gel.
"Of course, I believe in the team. We are not plotting a zig-zag course and we have set out to establish a new side. A revolution will take time. It is a serious situation, but not a crisis. (It is a false start) that we will now correct."
If the slump continues, Schalke will have problems securing a top three finish this season and securing their place in next season's Champions League, but Tönnies said he was unconcerned.
"The world won't fall apart, nothing will change for Schalke," he said.
Magath has admitted losing to Ruhr Valley rivals Dortmund was "unpleasant and distressing" last Sunday, especially after the home fans booed their side at Schalke's Veltins Arena.
"We have to get out of the uncertainty," said Magath.
"There was no alternative (to the upheavel in the team) if Schalke want to be champions in the coming years."