Holger Rune won his first ever ATP tour title on Sunday, but admitted it was the "worst way to win a final" after opponent Botic van de Zandschulp retired in the BMW Open final.

Both men were playing in their maiden tour-level final on debut at the ATP 250 event in Munich, and Rune becomes the third-youngest Munich champion in the Open Era.

Eighth-seed Van de Zandschulp was leading 4-3 in the first set, with his Danish opponent serving at 40-15 when the Dutchman retired due to an aching chest.

"This was probably the worst way to win a final,” Rune said. "I was obviously expecting a very tough match and he came out very strong.

"I just wish him all the best, a speedy recovery, and we all just hope to see him back on the court very soon."

Rune, who turned 19 on Friday, had a memorable week in Germany, including securing his first victory against a top 10 opponent when he beat world number three Alexander Zverev in the second round, before also getting past Jiri Lehecka, Emil Ruusuvuori and Oscar Otte on his way to the final.

"I'm super happy, of course," Rune continued. "As I said, not the way I want it to end, but if I look through the week, what a week.

"I played some unbelievable tennis, really fighting my way through it. To be playing here in Munich and winning my first ATP title in front of such a brilliant crowd, I couldn't really ask for more."