Karolina Muchova was crowned champion at the Bad Homburg Open, after Naomi Osaka withdrew midway through Saturday's final.

The Czech was a set and game to the good when the four-time champion was forced to retire with an ankle injury.

Osaka arrived in her first career grass-court final having not dropped a set in any of her four matches throughout the week.

However, she called a medical timeout after losing the opening three games inside 15 minutes, during which she was broken twice.

Osaka responded by getting her first game on the board, though her opponent quickly regained control by winning the next three to take the opening set.

Muchova, on her first appearance in Bad Homburg, then won the first game of the second, before sealing victory prematurely when Osaka signalled she could not continue.

Muchova continues momentum after Osaka's untimely injury

It was a disappointing ending to a breakthrough week for Osaka, who was appearing in the first grass-court final of her career.

The Japanese had lost all three of her tour-level finals since her most recent triumph at the 2021 Australian Open, and things did not look promising when she required treatment just three games into the championship match.

Just five games later, Osaka called it quits, and now faces a race to be fit for Wimbledon, which starts on Monday.

As for Muchova, the former French Open finalist is full of momentum ahead of her latest quest for a first major title.

Like Osaka, this was also the world number 11's first championship match on grass, and her third of a season in which she had already triumphed in Qatar.

Muchova, also a beaten finalist in Stuttgart, quickly established her authority on proceedings and, aided by Osaka's withdrawal, added further silverware to her collection.