During a particularly mischievous period of his life, many years ago, a 21-year-old Gaël Monfils returned home from a long night of partying at 5.45am and after a quick dash to the bathroom fell asleep. Minutes later he was woken up by a doping control officer at his front door: “I’m dying in my bed and somehow I hear the guy come. Barely. I’m dead and he’s coming,” says Monfils, laughing.

One of the requirements of being an elite player is providing your location for an hour each day as part of the anti-doping whereabouts system, which allows the anti-doping authorities to conduct unannounced out-of-competition doping tests. For years the Frenchman, like most other players, has assigned 6am as his usual hour, a time he is certain to be at home or in his hotel room.

On this occasion an exhausted Monfils opted for an unorthodox solution: “I say: ‘Bro, there’s no chance I [can] pee. I know you have to be with me. Come to my room.’

“I put down a chair. He was there and I said: ‘Sorry, I’m going to sleep. I don’t know when I’m going to wake up, but you can have a vision on me. It’s not that I don’t want to pee. I’ll be honest – I’ve been out. I peed like five minutes ago. I can’t.’”

It turned out to be a far longer nap than Monfils had anticipated: “I woke up at 3pm, the guy was scrolling his phone. [I say] ‘Hey, bro.’ I pee. So he was waiting for me for 10 hours. He could steal everything in my house.”

Along with training, fitness, matches and the relentless challenge of travelling to tournaments around the world, being a professional means navigating the World Anti-Doping Agency’s strict regulations, to which all athletes in Olympic sports must adhere. No matter how long it takes, every player must provide a urine or blood sample when called upon.

Once a player is selected for a test, the doping control officer must stay with the athlete and watch them at all times. That often means hosting a complete stranger in their home. Tallon Griekspoor, the Dutch No 1, recalls a time when a doping control officer spent three hours on his sofa: “We were rewatching an Ajax match for 90 minutes.”

Athletes can also be approached outside their chosen time, a source of irritation for some. If a doping control officer calls and they are in the vicinity of the location they provided the player is obliged to immediately return to the location. Last year, the talented Czech 19-year-old Jakub Mensik had to leave his high school graduation to go back home for a test. It took him three hours to produce a sample.

Taylor Fritz was once intercepted by a doping control officer in his Shanghai hotel lobby as he arrived from a long flight: “The guy was in my room and I was taking naps for 10 minutes at a time because I was so jetlagged and so tired. I kept on waking myself up every 10 minutes to see if I could pee because I couldn’t.”

The doping control officer is also required to watch athletes closely as they deposit their sample. The Frenchman Arthur Fils stresses the unusual nature of such encounters: “One stranger who is looking at you when you are peeing is pretty tough,” he says, laughing. “So every time it’s a weird situation.”

For Jack Draper, this has led to some particularly awkward experiences: “It’s a difficult moment, right? Sometimes you push so hard that you’re farting and you’re right next to them.”

Despite the unusual nature of these interactions, Andrey Rublev notes that players get used to them. Often seeing the same faces helps: “Sometimes if the guy is maybe a rookie or I have never seen him before, he will be a bit like a principal: ‘Now, put your pants down to your knees.’ I say, ‘Man, what’s the difference if it’s to the knees or not?’ He says, ‘No, these are the rules. Everybody has to follow.’

“Sometimes I face those guys, but it was maybe one or two times in my life. The rest, they are respectful, they are OK. They are there, they are watching, but they’re not trying to make you crazy.”

Draper often reminds himself that these encounters are less than ideal for all involved: “It’s a tough job for them. I always keep that in mind. Some people get annoyed because it is a very intimate situation. But I feel for that person. It’s their job.”

In the final weeks of the 2016 season, Madison Keys was chasing a spot in the WTA Finals. Hours after her semi-final loss in Beijing, Keys had already secured a last-minute wildcard into the Linz Open: “We ran to the hotel, packed and got on a plane two hours later and I forgot to update my whereabouts [to say] that I wasn’t going to be in Beijing – I was going to be on a plane. They came the next morning. I remember landing in Linz and immediately sobbing, like: ‘Oh no, I have a strike.’ It’s so stressful.”

Many players cite managing their whereabouts information as one of their biggest causes of stress, particularly in a sport that requires so much travelling and last-minute itinerary changes. However, it is a significant part of their job. Like many others, the British No 2, Cameron Norrie, works with his agent to manage his whereabouts: “We have a group chat and we screenshot [the app] every night, or he sends it, and we know exactly where it is going to be every night.”

Jessica Pegula, however, refuses to let anyone else handle her whereabouts: “I do it by myself. I just would never want someone else doing that because if they messed up, I’d be livid.”

Incurring one strike is far from unusual. During a recent period off the tour due to injury, Bianca Andreescu extended her trip in Thailand by one day, but forgot to change her whereabouts information. The next day she received a call from an official at her front door in Monaco.

Pegula says: “I know there’s a lot of girls that maybe messed up a couple dates and [were] on their second or third strike and they’re like, ‘That was the worst year of my life. I didn’t sleep. I was just laying in bed.’ You’re making sure the doorbell works. Every single phone is on. It can be very stressful.”

As with most other sports, numerous tennis players have been banned for whereabouts failures after missing three tests within 12 months. Recent examples include Mikael Ymer and Jenson Brooksby receiving 18-month suspensions in 2023. Brooksby’s ban was lifted early in 2024.

Keys thinks missing tests is far easier than most people believe. “It’s stressful, it’s hard,” she says. “I understand why it needs to be done, but it’s funny how it seems like a really simple thing, but to actually account for an hour, 365 days a year, every single year, you make mistakes.”

Fritz concurs: “It’s important that we have fair sport and people are able to get tested at random times. But the one thing I will say is people shouldn’t underestimate how just … shit happens.”