It's definitely a time for goodbyes.

For fantasy fans, life may never be quite the same after the end of Game of Thrones.

And if you're a Manchester City supporter, there is a Vincent Kompany-shaped hole in your affections as he leaves the club after 11 years to become Anderlecht player-manager.

It's hard to imagine the Belgian centre-back in any kit other than City's sky blue, but all good things must come to an end.

With that in mind, here are the other sportspeople we definitely won't be ready to say goodbye to when the time comes.

Lionel Messi and Cristiano Ronaldo

You're either 'House' Messi or 'House' Ronaldo, but let's cast aside the 'who's better?' debate for a minute and just imagine football without these two.

Messi, 31, has scored 602 goals in his 684 games for Barcelona, while Ronaldo, 34, has hit 600 goals in 804 games across his time at Sporting Lisbon, Manchester United, Real Madrid and Juventus.

That represents 0.75 goals per game for Ronaldo, and 0.88 for Messi - stats that leave the pair in a world of their own.

But what do we do after they retire?

Just sit watching reruns of Messi dropping Bayern Munich's Jerome Boateng on his backside during a Champions League semi-final? How about Ronaldo, then at Manchester United, smashing a 'knuckleball' free-kick past a despairing David James?

They may not be ready to bow out any time soon, but football won't be the same without them.

Serena Williams

With 23 Grand Slam singles titles to her name and having beaten 12 players who were ranked number one in the world - including her sister Venus, there is no doubt Williams is one of the greatest tennis players of all time.

She won the Australian Open while pregnant, then - after giving birth to daughter Alexis in September 2017 - returned to reach the Wimbledon final in 2018.

A pioneer for not only female athletes but black athletes as well, she has changed the landscape of tennis entirely.

In an article for Fortune.com she said: "Growing up, I was told I couldn't accomplish my dreams because I was a woman and, more so, because of the colour of my skin. In every stage of my life, I've had to learn to stand up for myself and speak out."

LeBron James

After scoring more than 32,500 points across 16 years, LA Lakers forward LeBron James is definitely a contender for the NBA iron throne.

Magic Johnson, Michael Jordan and Kobe Bryant were all worthy protectors of the basketball realm, but James has a very strong argument as to why he may be the greatest ruler of all time - the GROAT?

With 8,662 assists, 7,140 free-throws made and 4,163 turnovers in 1,198 games for the Cleveland Cavaliers, the Miami Heat and the Lakers, he has proved himself one of the most dominant athletes of his generation.

And it's not just his on-court heroics that have established him as a great. His I Promise School houses 240 at-risk third and fourth-grade students in James' hometown Akron, Ohio.

He may not have got the Lakers to the play-offs this season, but his legacy will live on well past his final game.

Marta

Brazilian striker Marta Vieira da Silva is a six-time winner of Best Fifa Women's Player.

The 33-year-old has scored 110 goals in 133 games for Brazil, and 166 goals in 257 games in her time playing at Los Angeles Sol, Santos, FC Gold Pride, Western New York Flash, Tyreso FF, Rosengard and Orlando Pride.

In an interview with BBC Newsbeat, former England manager Hope Powell said: "Her longevity in the sport and what she's done for it needs to be admired and respected.

"There are now opportunities for women to become professional footballers and earn a decent living from the game. There are lots of players that have made that pathway possible, and Marta is one of them."

The striker will play in her fifth World Cup this summer in France.

Roger Federer

The Swiss maestro has won 101 career singles titles - just the second man (after Jimmy Connors) to reach a century and the first for 36 years.

Federer's titles have come across 19 years, on all the sport's surfaces, in 30 cities and 19 countries.

And, at 37, he's still not letting up.

He pulled out of the recent Italian Open, but just six weeks earlier had told ESPN: "We're not thinking about retirement because I feel like the more I think about it, then the more they'll talk about it, the closer I am to it."

There will come a time when all six of these sporting greats will no longer be playing, and hopefully it doesn't leave a big Game of Thrones-size hole in our lives. But at least we can say we saw them at their best. After all, 'what is dead may never die'.