Serena Williams stayed relatively clear of the spotlight in between her injury-induced withdrawal from the 2018 French Open and her seeding announcement for the 2018 Wimbledon Championships, but there may have been some real rumblings behind the scenes.

No stranger to random drug tests, the 36-year-old tennis superstar was reportedly targeted for another one on June 14, roughly three weeks before her scheduled start of competition at Wimbledon. And according to Deadspin's Lauren Wagner, it didn't come without controversy, complete with an agent for the U.S. Anti-Doping Agency allegedly camping out at Williams' Florida home and refusing to leave until the Grand Slam veteran underwent an unannounced test.

A doping control officer showed up to test Williams at 8:30 a.m, when she was not at home. An assistant let the USADA officer into the home, and the officer refused to leave until Williams had been tested. There was a standoff; the test was not administered. Williams called Women's Tennis Association CEO Steve Simon to discuss the test and what she felt was unfair targeting.

As Wagner noted, the test was not administered. But it has since spawned, per the report, a statement from a Williams spokesperson condemning "invasive and targeted treatment" from the testers:

Over her 23-year career in tennis, Serena Williams has never tested positive for any illegal substance despite being tested significantly more than other professional tennis players, both male and female – in fact, four times more frequently than her peers. She has vocally supported, respected and complied with USADA testing throughout her entire career. While she willingly continues to submit to testing, there is absolutely no reason for this kind of invasive and targeted treatment.

For reference, as Wagner discovered via a USADA database, Williams has been tested five times in 2018 alone, whereas other top female players, such as Sloane Stephens (1), Madison Keys (1), Coco Vandeweghe (2), Danielle Collins (2), Alison Riske (0), Bernarda Pera (0), Taylor Townsend (0) and even Williams' sister, Venus (2), have all been tested on fewer occasions.

The USADA, meanwhile, has issued a statement of its own, per Wagner, saying it "retains the right to test any athlete at any time and may target test athletes as (it) deems appropriate."

In other words, the agent that may or may not have remained on Williams' property during the June 14 incident at hand would have been acting under USADA standards. But Williams, one of the most prominent faces of tennis history, may not be happy about it.

It also remains to be seen just who may have spread information pertaining to the June 14 test attempt. In 2016, for example, as Wagner noted, Russian hackers obtained World Anti-Doping Agency data and revealed that Williams was using a drug on a banned substance list, even though that drug had been approved for therapeutic use.