She's back: World No.1 Iga Swiatek made a winning return to the Hologic WTA Tour with a commanding Round 2 victory to open her title defense at the Porsche Tennis Grand Prix. 

Swiatek needed 1 hour and 26 minutes to defeat China's Zheng Qinwen 6-1, 6-4, extending her unbeaten run in Stuttgart to five matches. 

Swiatek moves through to a quarterfinal match against former champion and former World No.1 Karolina Pliskova, who outlasted Donna Vekic in 2 hours and 20 minutes, in a third-set tiebreak, to advance to the final eight. 

"I felt like I needed to be 100% focused from the beginning to the end, to think about technique and tactics," Swiatek said afterwards. "I'm pretty happy that I'm not rusty and I could perform good tennis, even though I had a break."

Read on for the top takeaways from Swiatek's comeback match.

Quick start, strong finish: Playing for the first time in 45 days, Swiatek hardly missed a beat to extend her head-to-head lead over Zheng to 3-0. 

She broke the reigning WTA Newcomer of the Year twice in each set to wrap up a straight-sets win, having been pushed to three sets by Zheng in each of their last three matches. 

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Swiatek didn't face a break point in her first seven service games, and was only pushed to deuce once, en route to building a 6-1, 4-2 lead. After Zheng captured back-to-back games with gritty play -- a scintillating backhand winner setting up her first break point of the match in the eighth game of the second set -- Swiatek had the answers to the challenge.

Challenge accepted: After denying Zheng two points for her first lead of the match, Swiatek broke her for a fourth time and served the match out to 15. 

"She's really talented, and everybody can see that," Swiatek said. "I needed to adjust, and I'm just happy that I was focused on myself, on what I wanted to do ... and I feel pretty comfortable. So I'm happy that I could show my good tennis."

Overall, Swiatek showed no signs of the rib injury that forced her out of the Miami Open and Poland's Billie Jean King Cup Qualifier.

'I'm not injured anymore': Swiatek looking to reset in Stuttgart

She landed 62% of her first serves in victory, winning 84% of those points.

Scouting Pliskova vs. Swiatek: Swiatek and Pliskova have only played once previously, but it was memorable. Swiatek won 6-0, 6-0 in the final of the Internazionali BNL d'Italia in 2021, a match in which she lost only 13 points. 

The two were expected to play in the quarterfinals of the Dubai Duty Free Tennis Championships this February, but Pliskova was forced to withdraw ahead of the match due to illness.

Haddad Maia advances after Rybakina retires with injury

No.14 Beatriz Haddad Maia advanced to her first Stuttgart quarterfinal after Wimbledon champion Elena Rybakina was forced to retire with a low back injury. After winning just one game in the first set, Rybakina called for a medical timeout in the second set. When play resumed, the Brazilian built her lead to 6-1, 3-1 before Rybakina walked to the net to shake hands and bow out.

Haddad Maia will face No.3 seed Ons Jabeur in the quarterfinals on Friday.