Two-time champion Simona Halep survived a second-set surge by one of the season's fastest-improving players, as she defeated homeland hope Sara Sorribes Tormo, 6-0, 7-5 in the Mutua Madrid Open first round.

No.3 seed Halep, who claimed the Madrid title twice successively in 2016 and 2017, needed an hour and 23 minutes to stave off a late challenge from the Spanish number two and improve to 26-7 at the event throughout her career.

Halep, seeking her 10th career clay-court title, saw a 5-1 second-set lead slip away as Sorribes Tormo fought back to 5-5, but she ultimately prevailed in the last two games to keep her hopes for a fifth trip to the Madrid final alive.

"She definitely played much better in the second set and she was more aggressive," Halep said, during her post-match press conference. "I lost a little bit of concentration at 5-1, and then I started to miss a little bit more. But even if I was a set and 5-1 up, I knew that she can come back. I expected a tough battle and it was."

The Romanian converted seven of her 13 break points en route to her second consecutive straight-set victory over Sorribes Tormo. Halep had previously defeated Sorribes Tormo 6-0, 6-4 in the first round of last year's Roland Garros.

Sorribes Tormo came into the event having had a superb first quarter of 2021, winning her first-ever WTA singles title in Guadalajara and rising to her current career-high ranking of World No.46. Her second-set comeback was stirring but the Spaniard could only muster up six winners in the match overall, compared to Halep's 21.

"I knew that she is with confidence very high because she played very well in the last months," Halep said. "I knew that it's gonna be tough because she likes the clay, and her spin is not easy to return. But I knew also that I have my chance, so I'm happy with the win."

Halep was very impressive on return at the match’s outset, cracking powerful winners with that shot to sweep to an early double-break lead at 3-0. The Romanian had no problems serving during that timeframe either, dropping just a single point on her service in the set as she clinched the bagel.

Sorribes Tormo at last got on the scoreboard with a break for 1-1, but Halep continued on her seemingly inexorable path to victory, breaking at love for 2-1, then repeating that feat with a forehand winner down the line for another love break and a 4-1 lead.

However, Sorribes Tormo found a forehand winner to break Halep when the No.3 seed served for the match at 5-2. Halep then held two match points on the Spaniard’s serve at 5-3, but both were lost -- the second with an untimely broken string -- and Sorribes Tormo held on.

Another break went the Spaniard’s way immediately thereafter, and after winning four straight games, Sorribes Tormo had surged back to level footing in the set at 5-5.

However, Halep came out on top in a number of grueling rallies in the next game to once again move ahead by a break. Serving for the match one more time at 6-5, Halep made no mistakes and held at love to earn the win.

"Coming to Madrid, always I have confidence because I like the courts, I like the conditions," Halep said. "I'm good. I'm happy to be here."

Next up for Halep will be Zheng Saisai of China, who ousted Poland's Magda Linette 6-2, 3-6, 6-1 on Friday. Halep has won both of her previous clashes with Zheng.

Two other Romanians were less fortunate than Halep, as they fell at the opening hurdle on Friday. First, Jessica Pegula defeated recent Istanbul titlist Sorana Cirstea, 7-6(5), 6-3, in an hour and a half.

Pegula, who reached the Australian Open quarterfinals earlier this season, was making her main-draw debut at the Mutua Madrid Open. The World No.33 improved to 18-6 on the year after ousting two-time Madrid quarterfinalist Cirstea, who won her first WTA singles title since 2008 last week in Turkey.

Daria Kasatkina also picked up a win over a Romanian who has had previous success in Madrid. She outlasted another two-time quarterfinalist, Irina-Camelia Begu, 4-6, 6-4, 7-6(1) in a three-hour barnburner.

Kasatkina, a two-time titlist already this season, failed to convert six match points at 5-2 in the final set, and a seventh at 6-5, before at last taking her eighth opportunity as she swept through the decisive third-set tiebreak.

But another former World No.1 joined Halep in the second round, as Victoria Azarenka outlasted Ekaterina Alexandrova, 7-5, 3-6, 6-1 in Madrid on Friday.

12th-seeded Azarenka, the Madrid runner-up in 2011 (lost to Petra Kvitova) and 2012 (lost to Serena Williams), needed just over two hours to quash the challenge from the hard-hitting Russian. Azarenka earned a victory in her first match since a round-of-16 loss to eventual champion Ashleigh Barty in Miami last month.

World No.32 Alexandrova used her flat, aggressive shots to stage a second-set comeback, but by the end, her 33 winners were outpaced by her 39 unforced errors. Meanwhile, Azarenka won over 82 percent of points returning the Russian's second service, en route to her second win over the Russian in their two meetings.

Azarenka advances past Alexandrova in Madrid 1st round: Highlights

After losing an early break advantage, Azarenka reclaimed her first-set lead with a backhand winner to break Alexandrova and move ahead 6-5. A passing winner gave the Belarusian a hard-fought first set, in which both players had more winners than unforced errors.

Azarenka twice found herself ahead by a break in the early stages of the second set, but each time, solid depth of return helped Alexandrova swipe the break back right away. Alexandrova then dominated the final games of the set with her powerful groundstrokes, scooping up the final four games to level the match at one set apiece.

Nevertheless, after an early exchange of breaks in the decider, Azarenka took command. The Belarusian won the final 10 points of the match, firing tremendously from both sides while the unforced errors from Alexandrova mounted.

A backhand winner closed out the match as Azarenka set up a second-round encounter with the aforementioned Jessica Pegula. Pegula won their only prior match -- in the first round of this year's Australian Open, spurring her on to the quarterfinals.