Serena Williams enjoyed one of the greatest tennis careers possible, having won 23 Grand Slam titles, losing another 10 finals.

Madison Keys emulated Williams at the Madrid Open, but it will take a long time for another player to reach the heights the latter once did.

Williams did, however, suffer a disappointing end to her career in terms of Grand Slam finals, of which she lost her last four.

The miserable run for Williams started at the 2018 Wimbledon final, where she was defeated by Angelique Kerber.

And that was followed by a 2018 US Open final loss to Naomi Osaka, a WTA clash which involved plenty of controversy.

Photo by Tim Clayton/Corbis via Getty ImagesPhoto by Tim Clayton/Corbis via Getty ImagesSerena Williams texted Patrick Mouratoglou after 2018 US Open final loss

Williams was adjudged to have been coached by Patrick Mouratoglou during the match, for which she was given a code violation.

The veteran was then handed a game penalty for calling umpire Carlos Ramos a thief and demanding an apology.

READ MORE: What Venus Williams said to Serena Williams at the net after she beat her for the first ever time in a Grand Slam final

She was then told post-match that Mouratoglou said he offered her advice, with Williams asked if she understood that or didn’t realise.

“So, I don’t know,” responded American icon Williams. “I literally just heard that, too, when they prepped me to come in.

Photo by Julian Finney/Getty ImagesPhoto by Julian Finney/Getty Images

“I just texted Patrick, like, what is he talking about? Because we don’t have signals. We have never discussed signals. I don’t even call for on-court coaching.

“I’m trying to figure out why he would say that. I don’t understand… I mean, maybe he said, ‘You can do it’. I was on the far other end, so I’m not sure. I want to clarify myself what he’s talking about.”

Photo by Michael Owens/Getty ImagesPhoto by Michael Owens/Getty Images

And when asked if the umpire had to give her the warning, she said: “No, because I wasn’t being coached.

“If I look at my box and they say, ‘C’mon’, or, ‘Good job’, I don’t know what else to do. After that I didn’t even look at my box anymore.”

Can Naomi Osaka get back to her best under Patrick Mouratoglou?

It was a bitter situation for Williams, who followed that final defeat with another at Wimbledon and another at the US Open before retiring.

Osaka meanwhile clinched her first Grand Slam title with the 6-2, 6-4 success in New York, her first of four such wins to date.

READ MORE: Rennae Stubbs thinks Naomi Osaka has done something ‘smart’ after losing early in Madrid as question asked about Patrick Mouratoglou

Result Year Tournament Opponent Score Win 2018 US Open Hard Serena Williams 6–2, 6–4 Win 2019 Australian Open Hard Petra Kvitova 7–6(7–2), 5–7, 6–4 Win 2020 US Open Hard Victoria Azarenka 1–6, 6–3, 6–3 Win 2021 Australian Open Hard Jennifer Brady 6–4, 6–3

Naomi Osaka Grand Slam finals

The former WTA number one, who incidentally is now coached by Mouratoglou, has failed to replicate those heroics since peaking, with the 27-year-old currently 55th in the world rankings.

Osaka shocked fans by playing the L’Open 35 de Saint-Malo, having taken on the WTA 125 event right after her early exit from the Madrid Open last month.