It's been another memorable year in sport, filled with incredible achievements and epic failures. We take a look at the most significant highs and lows from the year gone by.
Remarkably, there are several names that appear on both lists, which just goes to show how quickly things can go wrong, even when the most successful athletes and teams in the world are involved.
The Biggest Winners
1 Novak Djokovic
Novak Djokovic's 2015 season towers over most of the year's other sporting achievements.
Last year, the 28-year-old married his longtime girlfriend Jelena Ristic and celebrated the birth of his first child, and he would credit these developments in his personal life as being crucial to his success in 2015.
“Ever since I got married and became a father, I haven’t lost many matches, I won many tournaments. I suggest that to every player: get married, have kids, let’s enjoy this,” he quipped.
And who could argue. His achievements in 2015 were immense: three Grand Slam victories (the Australian and US Opens and Wimbledon), eight further ATP Tour titles (including the season-ending World Tour Finals,) over $20 million in earnings, and a 93% success rate in all matches.
2 Serena Williams
Over on the women's tennis tour, world number one Serena Williams more than held her own.
The American captured three Grand Slam titles (the Australian and French Opens and Wimbledon), came within an inch of the calender Grand Slam, won two further tournaments in Miami and Cincinnati, lost only three times out of 56 matches and banked more than $10 million in earnings.
3 Floyd Mayweather Jr.
Lover him or hate him, there's no denying that Floyd 'Money' Mayweather was incredibly successful in 2015.
The 38-year-old earned a staggering $220 million for his fight against Manny Pacquiao back in May, and while many were hoping he would face a serious challenge from the Filipino fighter, it turned out to be yet another one-sided contest.
The boxing public may have been the losers on the night, but Mayweather laughed all the way to the bank with nary a scratch on him.
He also earned another cool $32 million for his retirement fight against Andre Berto later in the year, but don't be surprised if 'Pretty Boy Floyd' returns to try and extend his 49-0 undefeated record at some point.
4 Tyson Fury
Staying with boxing, British heavyweight Tyson Fury's unanimous decision win over Wladimir Klitschko was another of the year's big success stories.
No one really thought Fury could end the Ukranian's nearly 10-year reign as world heavyweight champion, but that's exactly what he did, outfoxing and outboxing his veteran opponent to seal a huge result.
5 Holly Holm
This 34-year-old UFC fighter from Albuquerque, New Mexico became a household name overnight as she secured a massive upset victory over seemingly unstoppable bantamweight champion Ronda Rousey.
Holm totally dominated the contest and left Rousey, who some had been touting as the greatest fighter on the planet in the build-up to the fight, needing plastic surgery.
Certainly an upset that will go down in history.
It may be hard to believe now, but seven months ago, Jose and Mourinho and his Chelsea side were flying high after coasting to their fourth Premier League title by a comfortable eight-point margin.
It seems like only yesterday that Mourinho was strutting through interviews and press conferences in his trademark manner, vacillating between prideful boasts and bitter complaints and taunting the likes of poor Arsene Wenger with his success.
How quickly things can change.
7 Jordan Spieth
What a year for this talented newcomer, who rose to the top of the golf world rankings on the back of successive major victories at the Masters and US Open, top-four finishes at the Open and PGA Championships, and three further PGA Tour titles.
Spieth was only 21 when his meteoric rise kicked off with a win at the Valspar Championship back in March. What followed was a season he won't soon forget.
Even more frighteningly for his rivals, this young gun is only really getting started.
8 Jason Day
Though his season didn't quite reach the heights of Spieth's, it wasn't far off.
The Australian finally broke through with his first major victory at the PGA Championship in August, bringing to an end an at-times heart-breaking run of near misses in major tournaments.
Day also captured four other PGA Tour titles, and even briefly took possession of Spieth's world number one ranking, so spectacular was his form at one point.
How do you follow up winning your 23rd La Liga title? If you're Barcelona, you go on and win the Champions League too.
Coasting past Manchester City in the round of 16, thumping Paris Saint-Germain in the quarter-finals, easily dispatching the mighty Bayern München in the semi-finals and capping it all off with a resounding 3-1 victory away at Juventus in the final – no one could touch the Catalans in Europe in 2015.
10 Lewis Hamilton
English racing driver Lewis Hamilton underlined Mercedes' recent dominance in Formula One by storming to his second world championship in as many years.
Hamilton won 10 of the first 16 races of the year, putting himself in such a strong position that he was able to take his foot off the pedal as the season drew to a close and still coast to victory.
11 Golden State Warriors
While all eyes were on Lebron James and the Cleveland Cavaliers for the 2014-2015 NBA season, it turned out Steph Curry and the Golden State Warriors had other ideas.
The Warriors rose to prominence on the back of their star point guard's incredible shooting prowess and NBA great Steve Kerr's expert leadership, defeating the Cavs in the six-game playoff series to capture their fourth NBA Championship – and first since 1975.
They followed that up by winning their first 24 games of the new season – a new record in the NBA championship – and are hot favourites to defend their title next year.
12 Japan Rugby team
A special mention for Japan's national rugby side, who stunned two-time former world champions South Africa 34-32 in their opening pool match of the Rugby World Cup in England.
Even in a year of notable upsets, this one ranks as one of the most startling.
The chances of a Japan victory against the might Springboks were astronomical, but the planets must have aligned kindly for Eddie Jones' minnow side.
Japan sadly could not follow up that victory by progressing in the tournament, but the drama and emotion of that day in Brighton will not soon be forgotten.
The Biggest Losers
1 Jose Mourinho and Chelsea
Unfortunately, though Jose Mourinho and his Chelsea side were league winners only a few months earlier, their title defence now lies in tatters on the back of one of the worst runs in the club's recent history.
From his clash with team doctor Eva Carneiro, his seven-minute rant following a loss to Southampton and the numerous fines he received from the FA for his conduct, things could hardly have gone worse for poor Jose – never mind the string of losses his charges suffered on the pitch.
It all culminated with Mourinho's untimely exit from the club he helped put on the map. An ignominious end for 'The Special One' indeed, and it leaves the Blues in serious bother midway through the season.
2 Serena Williams
While she must be recognised for her incredible dominance in 2015, Williams makes this list because she tripped on the final hurdle just as she seemed destined for greatness.
Having won the first three Grand Slams of the year, the world number one found herself in the last four of the US Open, with only a couple of journeywomen Italians standing between her and a historic calendar Grand Slam – the rarest of achievements in sports.
Inexplicably, Williams lost to Roberta Vinci in the semi-finals, and her dreams of a Grand Slam went up in smoke. At 34, she may not get another crack at it.
3 Ronda Rousey
Coming back from a defeat as a fighter is always hard, but it's going to be even harder for former UFC bantamweight champion Ronda Rousey.
With a brand and persona based entirely on her supposed dominance and invincibility, Rousey's defeat to Holly Holm didn't so much puncture a hole in her public image as utterly obliterate it.
Ashamed to even show her face after the loss, Rousey must now find a way to return to the octagon and recover from her damaging knock-out – and to do so, she must find a way past the fearsome Holm in a much anticipated rematch.
4 Rory McIlroy
Rory McIlroy started the year as the undisputed best golfer in the world, but he finished it as seemingly the third best at most.
The Northern Irishman had to spend the majority of 2015 watching Jordan Spieth and Jason Day steal all his headlines – and eclipse him in the world rankings.
McIlroy did himself no favours either by injuring himself during a football match with friends right in the middle of the season – an error in judgement that would end up costing him dearly.
5 Floyd Mayweather
Another sportsmen who makes both lists, Mayweather may have made himself a very rich man in 2015, but he did his reputation absolutely no favours at all.
While he can't exactly be blamed for how little entertainment his fight against Manny Pacquiao provided, he can certainly be taken to task for waiting so long to agree to the bout in the first place, only facing the Filipino well after his prime, and choosing yet another lame duck opponent in Andre Berto to make his exit from the sport.
It was a fitting end for a man who has made a habit of not giving boxing fans what they want.
6 Wladimir Klitschko
Sticking with boxing, 2015 certainly won't be a year to remember for former Ukranian heavyweight champion Wladimir Klitschko.
Not only did the champion surrender all his belts after a 10-year reign, he did it to a man who arrived for their pre-fight press conference dressed as Batman.
Tyson Fury's victory was fairly resounding too, coming by unanimous decision, so Klitscko can only hope he manages to restore some semblance of pride when the two men meet in the ring for an already agreed upon rematch.
7 Suzann Pettersen
During September's prestigous Solheim Cup, the women's equivalent of the Ryder Cup, Sweden's Suzann Pettersen failed to concede a two-foot putt after American Alison Lee had picked up her ball on the 17th green.
Despite tears and protestations from the Americans, Pettersen refused to budge and concede the gimme. Unfortunately for her team, the ploy backfired spectacularly, as indignation in the US side quickly turned to fierce determination and resolve.
The incident ultimately sparked a tremendous US fightback, and saw Europe lose the cup, even as they were accused of unsportsmanlike conduct.
From being World Cup semi-finalists in 2014, the Dutch national football side would suffer a disastrous qualifying campaign for Euro 2016, crashing out of the tournament after finishing bottom of Group A.
An opening defeat against the Czech Republic in Prague was followed by two losses to Iceland and a disastrous 3-0 defeat in Turkey.
There was to be no turnaround from that point on, with a comical Robin van Persie own-goal in their 3-2 loss at home to the Czechs more or less summing up their qualifying run.
9 Michael Phelps
From Olympic hero to having several brushes with the law, Michael Phelps was banned for six months from all competition after being caught driving under the incluence of alcohol for a second time.
The ban started in late 2014, but to complicate matters, Phelps served his six months but was then prevented from taking part in the World Championships in August, despite returning to the pool in April – a bizarre decision by US officials that effectively curtailed his entire year.
He has now set his sights on the Rio Olympics in 2016, but can even the great Phelps bounce back from all the troubles he's had to contend with?
We're putting the entire sport on our list for finding itself mired in yet another doping controversy, this one seemingly more serious than ever.
With the likes of Russia and Kenya embroiled in widespread drugs scandals, an independent commission was set up to investigate doping in athletics.
Dick Pound, chairman of the commission and the former president of the World Anti-Doping Agency (WADA), says the world will be shocked when the final report is released in early 2016.
With an increasingly tarnished image, the sport must find a way to lift itself out of the doldrums before the Summer Olympics in Rio next year, although it may get worse before it gets better.