A tennis star successfully fights off a doping case. It’s still awkward.

And to state the obvious: it’s not great for tennis.

The fresh revelation that Jannik Sinner, the current men’s world No. 1, twice tested positive in March for trace amounts of a banned substance is an awkward bombshell on the eve of the U.S. Open.

This week the planet learned that the International Tennis Integrity Agency (ITIA) commissioned an independent tribunal to examine Sinner’s case, and it found Sinner—who denied intentionally using any banned substance—bore “no fault or negligence" for the antidoping violations.

Still, Sinner will be stripped of rankings points and money he earned while playing at March’s BNP Paribas Open in Indian Wells.

Jarring news, to say the absolute least. The optics and lingering questions are lousy for the tournament, the sport, the competitors—to say nothing of Sinner’s evolving image.

Sinner is one of the brightest young stars in tennis—a hard-hitting 23-year-old dynamo from Italy who won the Australian Open in January and a Cincinnati Masters 1000 tournament just the other day. He’s talented and likable, very much the type of player tennis hopes will carry the sport as the Roger/Rafa/Novak “Big 3" generation winds down.

Now he’s going to be hitting forehands under scrutiny, probably for a while.

On Tuesday, word arrived that Sinner took two separate tests in March which detected the presence of clostebol, an old-school anabolic steroid.

The amount of clostebol found in Sinner’s tests was exceptionally small—76 picograms per milliliter in the first test, 86 picograms in the second (a picogram is a trillionth of a gram). The ITIA’s outside tribunal cited expert testimony that, even if taken intentionally, such amounts wouldn’t have had “any…performance enhancing effect on the player."

Sinner’s explanation for the positive tests is this: During the Indian Wells tournament, he received repeated massages from a personal physiotherapist who was treating a cut on his (the therapist’s) finger with Trofodermin, an over-the-counter spray, purchased in Italy, which contains clostebol.

Sinner’s team contended that the physio accidentally transmitted the Trofodermin’s clostebol into Sinner, likely via wounds on the player’s legs. (Sinner has a skin condition, psoriasiform dermatitis).

Team Sinner surely knows it’s a bit much. My masseuse got an owie finger, used a spray with a banned substance, and passed it into my body during a massage.

You can hear the weary public rolling its eyes, even if there’s been recent research to support the contention that clostebol can be inadvertently transmitted through skin-to-skin contact, leading to cases of “accidental doping."

The ITIA and its tribunal accepted Team Sinner’s explanation that the presence of clostebol was unintentional. He wasn’t completely let off the hook—under “strict liability" standards, a player is ultimately responsible for what’s in their body, regardless of how it got there, hence the loss of earnings and points from Indian Wells.

Sinner released a statement saying he was “cleared of wrongdoing" and was looking forward to putting “this deeply unfortunate period" behind him. He’s expected to face the media at a pre-U.S. Open press conference on Friday.

That’s that? Well, not really. A few issues here:

Transparency/Fairness: Tennis is internally roiling about this case—even though Sinner was found to have “no fault or negligence," the world No. 1 being popped for a positive doping test is a massive story. Current and former players have wondered aloud about preferential treatment for a star—how Sinner’s case was settled so quietly behind the scenes when other positive tests have resulted in extensive public dramas and bans.

“Can’t imagine what every other player that got banned for contaminated substances is feeling right now," pro Denis Shapovalov tweeted. He added in a subsequent tweet: “Different rules for different players."

The most optimistic rendering of Sinner’s situation is: the system worked. The testing caught a positive, Sinner was (very briefly) provisionally suspended, the player was allowed to play while delivering a defense, the governing body accepted the explanation, and the damage was limited.

The key for tennis is to apply this standard and discretion evenly to all players, especially lower-profile ones who might not have the resources to mount a vigorous and immediate defense.

Strict liability: This is a thornier topic in antidoping, and not everyone agrees on the proper path. Again, strict liability refers to the idea that the athlete is ultimately responsible for everything that enters his or her body. And while guilty athletes almost always claim the ingestion was unintentional, the reality is that unintentional positives happen.

It’s why there’s a growing belief that for certain banned substances with a track record of accidental positives—and clostebol appears to be one—the minimum standard should be raised.

Any positive test would still be reported and trigger monitoring, but the minimum to commission a full-blown investigation and demand an athlete’s explanation would be raised. The idea isn’t leniency, but avoiding costly, career-altering dramas for minuscule, unintentional positives.

Sinner’s road ahead: Sinner has his work cut out for him. Friday’s press availability will be key. He’ll likely be asked to detail both his explanation and the timeline, and given the behind-the-scenes nature of his case and its dispensation, it’s essential that he’s forthcoming.

There will be questions about his physio and his team—how could people experienced in administering to professional athletes, presumably aware of antidoping hazards, have this happen?

For Sinner, it’s surely a nightmare. He has prevailed in his defense, but the U.S. Open will be a test of the public’s reaction. As the world No. 1, Sinner will be the tournament’s top seed. Chatter will follow him throughout, and not the kind of chatter he wants. What sort of impact will this have on his play?

It’s not great. Not great for tennis—or Jannik Sinner, or anyone.

Write to Jason Gay at Jason.Gay@wsj.com