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The US Open champion fell to a third consecutive defeat, after a sequence of 17 straight wins, as she quit the Purple Group clash with Pliskova after losing the first set 6-3.

Andreescu had been badly hobbling since early in the match when she "heard a crack" as she returned the ball while up a break.

She initially refused to retire but, speaking afterwards, having confirmed her intention to have an MRI on Thursday, the 19-year-old was content with her decision.

"I stepped weirdly on a return," Andreescu said. "I heard my knee crack. It kind of went inwards.

"Putting pressure afterwards on it really bothered me. I could barely bend my knee. But I fought with the pain as much as I could. 

"At some point, an athlete has to say, 'Stop', and just listen to their body. That's what I did.

"It's disappointing because this is the last tournament of the year, so you want to go all out. You're playing one of the biggest tournaments of the year, too. It's not easy.

"I've never had a during-match injury happen before - other than spraining my ankle, but that was back in 2015.

"Honestly, I really didn't know what to do. I've fought through pain before, but this was different. It was like very acute.

"But it's the last tournament of the year. I just told myself, 'Push it as much as you can. You're going to have a good break after this.' Maybe I could have pushed it more. I don't know. 

"My team said no. It was good that I stopped. Honestly, I could have kept going. If I did, then I would just be whining on the court. I don't want that. I've done that enough."

Andreescu's defeat to Pliskova saw her hopes of progress end at the season-ending WTA Finals, meaning she can decide whether to face Elina Svitolina, who is already through, to conclude her breakout campaign.

Canadian Andreescu won titles in 2019 at Indian Wells, the Rogers Cup and Flushing Meadows, climbing to number four in the WTA rankings.