Stalmach learned his trade at Górnik Zabrze before moving to AC Milan's youth academy in 2022. He joined Magdeburg in the winter of 2025 and made 28 appearances across the second division, the Regionalliga and the DFB-Pokal during his time there.
Werder Bremen's head of professional football Peter Niemeyer outlined why the club had tracked Stalmach for some time.
"Dariusz is an exciting, ambitious player whose development we have been following for a while," Niemeyer said. "We see further development potential in him and want to work with him to expand his abilities."
Head coach Daniel Thioune was equally positive about the addition while managing expectations around a player who is still finding his ceiling.
"Dariusz is technically strong and has not yet reached the end of his development," Thioune said. "It is therefore important to frame expectations around him correctly. He will definitely enrich our squad and I am looking forward to working with him."
Stalmach himself expressed eagerness to take on the challenge of the Bundesliga.
"I am really happy to be able to make this move to Werder and to take on this challenge," he said. "I can't wait to play in the Bundesliga and above all in the Weserstadion."
The signing is the latest in a productive window for Werder, who had already brought in several players before Stalmach's arrival. For a club looking to build depth in their midfield ahead of a new Bundesliga season, the addition of a 20-year-old with an AC Milan background and proven second division experience represents a considered piece of business.
Stalmach's willingness to push for the move suggests a player with the ambition to match the opportunity, which is exactly what Thioune and Niemeyer outlined when describing what drew them to him.