"Don't blow the whistle yet," BVB coach Niko Kovac instructs the referee over Niklas Süle

Niko Kovac was determined to keep his promise, so he quickly reached an agreement with referee Patrick Ittrich.

"Listen: don't blow the whistle until I've brought Niki on," the Borussia Dortmund manager reportedly told the referee the day before the 3–2 (2–1) win over Eintracht Frankfurt. The plan worked: Niki—Niklas Süle—came on in the 88th minute of his final home game for BVB.

"It was five or six minutes. He deserved it," Kovac said of the 30-year-old, who will retire this summer. "He's had a fantastic career. I wish him all the best in his retirement; he'll be playing a lot of golf and probably travelling the world."
The former international, whose contract is expiring, announced on Thursday that he is nearing the end of his career. "I'm delighted with the send-off," the defender told Sky. "A perfect day, a perfect setting, and the fans were fantastic. It was great that the manager gave me a few extra minutes for my 300th game, and my entire family was here."

Kovac keeps his word and brings on Süle: "He's earned it"
It was also the final home game for Julian Brandt and Salih Özcan as BVB professionals. Unlike Süle, however, the pair are not ready to hang up their boots just yet.
Ittrich, the Hamburg-based referee, will also hang up his whistle when the campaign concludes.