SHENZHEN, China - Maria Sharapova was pushed to the brink by American Alison Riske at the Shenzhen Open on Tuesday night, but the Russian rallied from a set and a break down to advance to the quarterfinals, 3-6, 6-4, 6-2.

A two-time runner-up in Shenzhen in each of the past two years, Riske used precise, accurate hitting to move Sharapova aound the court en route to building a 6-3, 2-1 lead, as she looked for her first career win against the former World No.1. 

Nonetheless, the five-time Grand Slam champion rallied to win five of the last six games to knot the match at one set apiece, before winning the last four games of the match to rach the last eight in just under two and a half hours.

"I'm glad I got this kind of match. Although I would've wanted a quick and easy victory, these are the kind of matches that you need, especially with such a short preparation going into the Australian Open in terms of match play," Sharapova said on-court after the match.

"I'm just glad that I came back, she played a really great match and as I said to her at the net, I thought it was a great quality match. In the end, I won it so I have another opportunity to keep going."

Blasting 34 winners, nearly three times Riske's total, Sharapova's effort was buoyed by 11 aces, as the Russian saved seven of the 10 break points she faced overall.

After getting the second set back on serve in the fourth game on her fourth opportunity, Sharapova was forced to save three break points which would've seen Riske reclaim her lead.

Navigating through that service game successfully enabled the World No.59 to take her first lead in the encounter, but the key break that decided the set came in the eighth game.

The Russian was later forced to save a pair of break points in the final game - two of the five total that she saved in the set - to level the match, and held off the World No.70's attempted comeback in the decider.

A break in the first game of the match gave the American a lead she never relinquished for the duration of the opening set.

Though Sharapova never faced a break point in any of her next four service games in the first, she was unable to take a toal of three chances which would've drawn her level in the opener.

Riske saved two break points at 15-40 in the fourth game, and saved another in the sixth, grinding out both holds as they went to deuce, evenutally wrapping up a one-set advantage in three quarters of an hour. 

Sharapova's momentum continued into the decider, and she would not be denied despite seeing four break points go unclaimed as Riske held to begin the final set. 

The American surrendered serve in the third game, and though she briefly drew level again, breaking back with the help of a double fault from Sharapova, blistering winners from the Russian's racquet saw her earn two more breaks of serve in the final four games of the match.

Sharapova will face Kazakhstan's Zarina Diyas in the quarterfinals, who came through a marathon match of her own against Chinese No.3 seed Zhang Shuai earlier in the day.

Diyas built herself leads of 4-0 and 5-1 in the second set tiebreak as she looked to close out the home favorite in straight sets, but eventually needed a decider and two hours, 22 minutes to score the upset, 6-3, 6-7(5), 6-4.