Borussia Dortmund midfielder Sven Bender described the club's pre-season training under new coach Thomas Tuchel as "fun but exhausting" ahead of the UEFA Europa League qualifier against Austrian side Wolfsberger.
Bender, 26, is embarking on his sixth season as a Dortmund player and he will be playing under a new manager for the first time.
Tuchel's first challenge as Dortmund coach is to take his new charges to Wolfsberg, where they meet the fifth-placed team from last season's Austrian Bundesliga.
Bender told the club's official website: "The coach is extremely detailed and tries to give us everything.
"It makes a lot of fun, but also exhausting. You will be clearly criticised if you have to do something better."
On the Europa League qualifying matches, Bender added: "We can also use these games to bring security. Then this very early start to the season can have a positive aspect for us."
Dortmund left-back Marcel Schmelzer said his teammates were adapting well to the new tactical approach under Tuchel, saying: "It is a different system, but the basic things do not change.
"The game remains the same, the focus is different."
Wolfsberger defeated Shakhtyor of Belarus over two legs to set up the clash with Dortmund, but Schmelzer is determined to see off the Austrians, saying: "The goal is to move into the group stage. You almost do not care who you play, but of course the trip to Austria is more pleasant than to Belarus."
The fixture could also see Dortmund hand debuts to their trio of close-season signings.
Tuchel has recruited midfielder Gonzalo Castro from Bayer Leverkusen for a reported €11million, while Julian Weigl has arrived from 1860 Munich and Roman Burki has been acquired from Freiburg.
All three new arrivals played some part as Dortmund triumphed 2-0 over Dortmund in a friendly on Saturday.
Dortmund must face both legs of their qualifier against Wolfsberger before their domestic campaign begins on August 15, at home against last season's third-placed Bundesliga finishers, Borussia Monchengladbach.
