STUTTGART, Germany — Canadian teenager Felix Auger-Aliassime will play Italy's Matteo Berrettini in the final of the Stuttgart Open.

The 18-year-old Auger-Aliassime, from Montreal, progressed to his third tour-level final without playing on Saturday as compatriot Milos Raonic withdrew ahead of their semifinal due to back problems.

"It's just tough to see Milos having to withdraw," Auger-Aliassime said on court. "He's one of the best guys on tour. He's always been great to me since I first arrived on tour when I was a junior.'

"It's tough to see him go out that way but at the same time it is what it is and I have to try and get ready for tomorrow's final as best as I can."

The sixth-seeded Raonic, from Thornhill, Ont., lost last year's final to Roger Federer, who opted not to defend his title.

"It's hard for me to accept this situation but it is how it is," Raonic said. "But I'm happy that Felix has an opportunity to win his first title, so I wish him all the best."

Raonic was playing his first tournament since suffering a knee injury in March. The hard-serving 28-year-old has battled the injury bug throughout his career.

Auger-Aliassime also is returning from injury as a left abductor problem forced him to miss the French Open.

The 21st-ranked Auger-Aliassime previously reached championship matches in Rio de Janeiro in February and the Lyon Open in May — both on clay.

Berrettini defeated Germany's Jan-Lennard Struff 6-4, 7-5 in the other semifinal. The 30th-ranked Berrettini will be going for this third tour title and his first on grass after victories in Budapest in April, and Gstaad, Switzerland, last year.

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— With files from The Canadian Press.