NEW YORK, NY, USA - 2006 champion Maria Sharapova knocked out the No.2 seed Simona Halep in a three-set thriller to close out a blockbuster Day 1 at the US Open.

Only a handful of points separated the pair as Sharapova, into the year’s final Grand Slam on a wildcard, weathered a second-set letdown to outhit the World No.2, 6-4, 4-6, 6-3 after a marathon two hours and 44 minutes.

Read more: Insider Live Blog: Simona Halep and Maria Sharapova face off on Day 1

The victory extends Sharapova’s streak to 23 consecutive first-round Grand Slam victories, 11 of those coming at the US Open, where she remains undefeated in the opening round.

But for Halep, the loss ends her bid for a maiden Grand Slam title - as well as derails her fifth chance of the season to become the WTA World No.1.

“It's all worth it. You sometimes wonder why you put in all the work. And this is exactly why."

- Maria Sharapova

“You never really know what you're going to feel until you win that match point and you can't control what's going to go through your mind,” a tearful Sharapova said in her on-court interview. “It's all worth it. You sometimes wonder why you put in all the work. And this is exactly why."

"We respect each other so much and I know when we both saw the draw there was something extra for that. The hype was because of the quality of the matches we've played before. No matter what my record against her, it's always been tough."

Sharapova came into the tournament having played just one match since her return to tennis in May, as injury woes kept her away from the courts most of the summer, but heartened by a 6-0 lead in her head-to-head against Halep.

The Russian earned the first break after a couple of tense opening games, with both players thoroughly examining each other’s game. Sharapova dodged a break point in a marathon third game, but grabbed the first break in an even longer next game after a flurry of monster returns brought up three chances.

Halep broke straight back to keep them on serve, stepping in and raising her aggression. She finally held serve after four consecutive breaks of serve showed the best of the pair’s differing styles, with Sharapova firing on her aggressive attacks but running up against Halep’s rock-solid defense. Sharapova finally broke through in the final game after holding serve to take the first set.

She carried all of that momentum into the second, getting the first break early on and consolidating to a daunting 4-1 lead as Halep’s first serve percentage started to take a dip. But Halep stayed solid and a series of Sharapova errors rewarded her patience with a break back.

Despite dropping the set from such an advantage, Sharapova recovered brilliantly and showed all of her famous grit to break early once more and grab a quick 3-0 lead. Halep never recovered and, though she had points to level the score and break back as Sharapova was serving for the match, she couldn’t convert as the wildcard took her spot in the second round.

For Halep, the loss ends her bid for a maiden Grand Slam title - as well as derails her fifth chance of the season to become the WTA World No.1.

“It was very was very tough, not like first-round matches. But this is the draw. I think I give everything I had. She was better."

- Simona Halep

“I'm sad, of course, losing this match,” Halep said afterwards. “But I think I give everything I had. She was better. She was serving better. My serve was very bad today.

“It was very tough, not like first-round matches. But this is the draw. I cannot say anything else, just that's it. It's the luck. It was a tough one for first round, for sure. But still I think I played okay, she played really well. It was a good match.”

Up next, the Russian takes on the big-serving Timea Babos, who defeated Viktorija Golubic in a similarly close three sets earlier in the day, 7-5, 5-7, 7-5.