Madison's Avenue: Keys Into 4th Round

© 2017 Michael Cummo/BNP Paribas Open

For Madison Keys, four months felt like an eternity. A left wrist injury had led to arthroscopic surgery, which in turn led to the longest layoff of her young professional career, an agonizing stretch that would include sitting out the 2017 Australian Open.

"I couldn't do anything," confided Keys, whose surgery came just three days after the 2016 WTA Finals in Singapore. "For the longest time, I still couldn't turn my steering wheel and I couldn't use my left hand doing this and that. It was tough and it was really stressful. There were so many times when I'd be fine for a week or a month, and then all of a sudden I'd be, 'Oh, my God, guys. What if I never win a match again? What if it's over?'"

The 21-year-old, who enjoyed an otherwise successful 2016, a year in which she became the first American to make her Top-10 debut since Serena Williams in 1999, says she leaned heavily on family, friends and her team, which once again includes three-time Slam champ Lindsay Davenport.

WATCH: KEYS SHOT OF THE DAY

Thus far, she's made a seamless return to the court here in Indian Wells. All she’s done is top Colombia’s Mariana Duque-Marino 6-1, 7-5 and Japan’s Naomi Osaka (in a rematch of their epic US Open clash of 2016) 6-1, 6-4 in reaching the Round of 16.

"Not very high," said Keys of her expectations coming into the BNP Paribas Open. "I was, like, 'If I get a set, I'll be happy.' It's always tough to come back and everyone is in the middle of their season. I definitely had really low expectations."

Regardless of whether she wins another match here -- next up is former world No. 1 Caroline Wozniacki -- she’s just happy to be striking tennis balls again, testing her considerable skills against the game’s elite.

"It definitely made me appreciate it a lot more," she said. "The end of the season, from US Open on, was really tough for me. Everything was painful, and it was really hard to just get myself out there and keep practicing and keep doing it. Being in Singapore was great, but it was also, like, ‘God, this is a grind. I can't wait to get to the finish line.’ Now, being able to hit pain-free, it's great. So that's definitely been a big blessing for me."