Mainz were missing eight players through injury as they drew 1-1 in a friendly with third division Offenbach,
"We have hit the lowest point in our preparation in terms of physical condition," Tuchel was quoted as saying by Kicker magazine.
"Therefore, I have to see things very realistically - that means it was as bad as it looked."
In addition to the eight absentees, Mainz will be without Sami Allagui next weekend as he plays for Tunisia in the African Nations Cup.
"I just hope that all of our injuries are minor," added Tuchel. "It's really hit us hard."