MIAMI, FL, USA - No.21 seed Anett Kontaveit advanced into the Miami Open quarterfinals when BNP Paribas Open winner Bianca Andreescu was forced to retire due to a right shoulder injury, trailing the big-hitting Estonian, 6-1, 2-0.

"I guess this is just a way of my body telling me that it's had enough," Andreescu explained after the match. "It's disappointing, but it's part of the sport."

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"She's had so many matches, and I'm sure she's fatigued," Kontaveit said. "She's had such a great run, and I give her a lot of respect for that. I think I did everything I could have really well today."

Andreescu had won a 10th straight match early Sunday morning when the Canadian teenager, in a rematch of the Indian Wells final, knocked out reigning Wimbledon winner Angelique Kerber for the second time in two weeks.

Playing for a second consecutive Premier Mandatory quarterfinal, Andreescu - who dealt with right shoulder tightness in her last match - called a medical timeout after dropping the first set, ultimately ending the contest with Kontaveit after 56 minutes on Court 1.

The match initially began on even footing as Kontaveit held serve to open and Andreescu held a game point before a rain delay interrupted play for almost 90 minutes.

"The clouds looked pretty bad when we were walking on court, so I guess I was expecting it a little bit. But I just had something a little to eat, changed my clothes, and had to warm up again."

Upon resumption the Estonian, who won a titanic three-set thriller of her own against Ajla Tomljanovic out on Court Butch Buchholz Saturday night, took control, taking a 3-0 lead and saving break points to maintain her advantage early in the first set.

"I had really tough two first matches. They were both tough, tough battles, and I was really pleased with the way I fought in those two tiebreaks, especially against Ajla, and I thought I played a good match to get through that.

"I actually felt like I was playing good tennis already at Indian Wells, and I had a really, really tough match against Karolina Pliskova. I actually thought the level was really good, and she served extremely well in the third set. I'm pleased with the way I have been playing these last couple of weeks."

Six games from the best Premier Mandatory result of her career, Kontaveit broke serve again to take the early lead in the second. The match came to its untimely conclusion shortly thereafter, as Andreescu couldn't continue.

Up next for Kontaveit will be either Hsieh Su-wei or former World No.1 Caroline Wozniacki.

"She's such a great mover," she said of Wozniacki. "She brings so many balls back. The point's never over with her until the ball bounces twice, so you have to work really hard for every point."

Kontaveit briefly shared a coach with Hsieh, and enjoyed many an off-beat practice session with the tricky veteran.

"I actually enjoy watching her matches a lot. She mixes it up so much, and she's fun to watch. She's done really great. It's tough to find your rhythm against her, but whoever wins, I'll have to play really well to get through it, anyway."