NEW YORK CITY, NEW YORK: Serena Williams appeared to serve a not-so-subtle dig at her former rival Simona Halep, who has been banned from tennis after testing positive for the banned substance Roxadustat at the 2022 US Open.

The 31-year-old Romanian star, who has been provisionally suspended since October 2022, was found to have violated the sport's Anti-Doping Program on two separate occasions and handed a four-year ban.

After Halep's suspension was upheld, Williams took to Twitter to share a no-context message that read, "8 is a better number."

The tweet was likely in reference to the 2019 Wimbledon women's singles final, where Halep thwarted Williams' dreams of winning her eighth title.

Williams' husband, Alexis Ohanian, also spiced things up by retweeting a photo of himself wearing a t-shirt that read: "Keeping kids off drugs," according to Yahoo News.

The entrepreneur originally wore the Savage t-shirt back in 2019 when his wife faced Maria Sharapova. This caused a stir at the time as the Russian star was banned for 15 months after failing a drug test in 2016.

"Some fashion is timeless,” Ohanian wrote in the caption to which Williams replied, "Seriously not out of style."

Why was Simona Halep banned?

Halep, a two-time Grand Slam champion, was banned from competing after testing positive for the prohibited substance Roxadustat at the 2022 US Open and was also subsequently found to have irregularities in her athlete biological passport following the analysis of 51 blood samples.

Roxadustat is a medication that is approved for the treatment of anemia, but it is prohibited by the World Anti-Doping Agency since it is thought to be a blood-doping agent that boosts the formation of red blood cells and hemoglobin.

"The ITIA has followed the proper processes as we would with any other individual —in accordance with the World Anti-Doping Code— fulfilling our purpose and responsibility to uphold the principle of fair competition, on behalf of the sport," said Karen Moorhouse, the CEO of the ITIA.

Roxadustat was discovered in a urine sample taken from Halep at the 2022 US Open. The Romanian athlete stated that the substance was discovered in her blood because of a tainted supplement that she had taken before the championship.

Still, the ITIA asserted that "the volume the player ingested could not have resulted in the concentration of roxadustat found in the positive sample."

Later, the expert group evaluating Halep's Athlete Biological Passport also determined that the evidence of doping was strong enough to charge her with the anti-doping violation.

"The ABP charge was also upheld, with the tribunal stating that they had no reason to doubt the unanimous 'strong opinion' reached by each of the three independent Athlete Passport Management Unit experts that 'likely doping' was the explanation for the irregularities in Halep's profile,” Moorhouse added, according to CBS.

How Simona Halep reacted to her suspension

In a statement posted on social media, Halep "refused to accept the decision,” stating that she would appeal the suspension.

"The last year has been the hardest match of my life, and unfortunately my fight continues. I have devoted my life to the beautiful game of tennis," she wrote.

“I take the rules that govern our sport very seriously and take pride in the fact I have never knowingly or intentionally used any prohibited substance. I refused to accept their decision of a four-year ban,” she added.

She went on to clarify that the Roxadustat must have been discovered as a result of a recent modification to her dietary supplements, which did not include any illegal chemicals but may have been tainted.

"I am continuing to train and do everything in my power to clear my name of these false allegations and return to the court," she said in a statement.

The former World No 1 also stated that she would fight to clear her name and would "pursue all legal remedies against the supplement company in question."

Halep also took a dig at the federation, saying, "The ITIA relied solely on the opinions of these experts who looked only at my blood parameters - which I've maintained for more than 10 years in the same range.”