The club lost star forward Isco to Real Madrid in June and have since struggled to find replacements, with only Polish striker Bartlomiej Pawlowski and former Manchester City forward Roque Santa Cruz brought in to fill the void.
And while Schuster says he is happy to have captured former loanee Santa Cruz on a permanent deal, he is worried by the lack of creative players surrounding the Paraguayan.
"We must work on the subject of attack and the problem is not the number nine, but those around him," he said.
"I want Roque to have six chances and if he only manages two, then I worry, but it’s not his fault, because there are not those around him as I would like.
"That’s where we have to work, to have more presence and imagination in attack."
Schuster also confidently predicted that the season-long loan of 20-year-old Pawlowski from Widzew Lodz will help improve his attacking options.
"I have watched him for a year, but I first wanted to see what we had here because I like to sign players who can do better than those already at a club," he said.
"He can help with his characteristics, playing around the area."
