Thomas Tuchel expects a tough test for Borussia Dortmund on Sunday, when Mainz will seek to further disrupt the Bundesliga title race.
Mainz are in the hunt for Champions League qualification and underlined their impressive form earlier this month by securing a shock 2-1 win at leaders Bayern Munich.
On the back of that triumph, which allowed Dortmund to trim Bayern's advantage at the summit to five points, Tuchel predicted a dogged showing from his former employers at Signal Iduna Park.
"Even without the result against Bayern it was clear to see how well Mainz have played this season," the Dortmund boss told his pre-match news conference.
"You need a special spirit to beat Bayern. We didn't need [to see that result] to know how difficult a task it will be on Sunday.
"It's possible that Mainz will defend with a back five. They played a 5-4-1 in Munich. It is our job to deal with Mainz's aggressive and brave defending."
Dortmund were in dazzling form when they claimed a 3-0 first-leg victory over Tottenham in the last-16 of the Europa League on Thursday.
Tuchel stuck with a largely first-choice XI as a much-changed Spurs side were duly punished but the coach does not feel the need to rotate his line-up excessively this weekend, despite influential midfielder Ilkay Gundogan being set to miss out once more due to a foot injury.
"I haven't given much thought to the rotation of the squad," he added. "We were very fresh against Tottenham.
"There are some of our players who are playing at their limit in terms of intensity."