However, the German believes the 27-year-old will become the 'perfect striker' for the Cottagers once he regains match fitness.
"Ross came to us with a lack of fitness and not at the beginning of pre-season. He is not at the same level as the rest of the players," Magath said.
"I wanted him to be fit when we signed him but at the moment he is not in the right shape. When he does, he will be the perfect striker for us."
In other Fulham news, goalkeeper Maarten Stekelenburg has joined Monaco on a season-long loan deal.
"I am happy to be a part of the project of the club. I am fully going to give myself for my new colours," he said.
Glenn Hoddle could finally be set for a return to coaching - but not as a no.1
According to the Sunday People, Harry Redknapp is keen on bringing the former Tottenham and England boss on board as first-team coach.
The paper also claims that Hoddle could be a long-term replacement for Redknapp should be step down due to health reasons.
Hiring the 56-year-old may be resemblant of the decision appoint Steve McClaren as a coach last season, before he left to become Derby County manager.
The Argentine midfielder was initially linked with Spurs - and then Leicester. However, the Rs have now been tipped to approach the 33-year-old, who left Inter Milan this summer.
Lassana Diarra is also said to be a target for Redknapp.