As the 2025 Grand Slam season kicks off at the Australian Open, tennis remains gripped by lingering questions over doping, with Jannik Sinner and Iga Swiatek’s cases still unresolved.

Both players, who dominated 2024 as world No. 1 in their respective categories, are at the center of controversy, adding another layer of intrigue to this year's tournament.

Sinner, defending his Australian Open title, holds onto his No. 1 spot in the ATP rankings despite two positive tests for trace amounts of anabolic steroid Clostebol in March.

The International Tennis Integrity Agency (ITIA) cleared him after deeming the contamination accidental, a result of a trainer's use of the substance.

However, the World Anti-Doping Agency (WADA) has appealed the decision, seeking a one-to-two-year ban.

A final ruling is expected after the Australian Open. Sinner, who had a standout 2024 season with eight titles, including the U.S. Open, and led Italy to the Davis Cup, expressed confidence that the matter will be resolved in his favor.

"It’s in my head a little bit," he admitted, adding, "but I’m confident everything will go my way."

Swiatek, who has spent much of the past three years as the world No. 1 on the WTA tour, also found herself embroiled in a doping issue.

In late November, she accepted a one-month suspension after testing positive for a banned heart medication, TMZ.

The ITIA accepted her explanation that the positive test stemmed from the contamination of melatonin, a nonprescription sleep aid she had been using.

Swiatek’s suspension kept her out of three tournaments, and the issue only came to light after the season ended.

"This whole process was pretty abstract sometimes and hard to understand," Swiatek remarked.

While many in the sport have stayed tight-lipped on the cases, some have voiced concerns.

Novak Djokovic, a 24-time major champion, raised questions about the disparity in treatment of Sinner and Swiatek compared to other players in similar situations.

Simona Halep, who was banned for four years after testing positive for Roxadustat but later had her suspension reduced, also expressed frustration over the handling of Swiatek’s case. "I can’t find, and I don’t think there can be a logical answer," she said.

The doping cases have not gone unnoticed by players like Nick Kyrgios, who blasted the handling of the situation. "Two world No. 1s, both getting done for doping, is disgusting for our sport," Kyrgios said. "It’s a horrible look."

Meanwhile, the doping issue has yet to overshadow Sinner's impressive 2024 season.

With a 73-6 win-loss record, he heads into the Australian Open on a 14-match winning streak. Despite the ongoing doping controversy, Sinner’s dominance is clear.

On the doubles side, Max Purcell, who won the U.S. Open men’s doubles title in September and was a two-time Australian Open runner-up, found himself involved in a doping case of his own.

Purcell did not test positive but accepted a provisional suspension for receiving an IV infusion of vitamins above the allowable limit.

His doubles partner, Jordan Thompson, voiced his frustration: "It is a joke."