The UFC featherweight champion posted the snap of himself holding up a certificate from the United States Anti Doping Agency (USADA), presumably a response to McGregor's past insinuations that the Brazilian had used performance enhancing drugs.
UFC returns to London and Michael Bisping, Brad Pickett and Ross Pearson are hoping to feature at O2 Arena show in February
Ronda Rousey thrills Australian UFC crowd ahead of her 'biggest challenge' against boxing world champion Holly Holm at the Etihad...
Conor McGregor could be the UFC's best featherweight but I can still beat him, says fellow Ultimate Fighter coach Urijah Faber
Paige VanZant in no hurry to carve her name into UFC history books ahead of duel with Alex Chambers on Saturday
Life's a beach for UFC star Conor McGregor as heavily-inked fighter shows impressive balance ahead of Jose Aldo rematch
Ronda Rousey goes shopping with friends as UFC star is all smiles after saying 'yes' to military man who asked her to the Marine...
Conor McGregor lives up to 'notorious' nickname by adding more tattoos to his heavily-inked body while out in California
Conor McGregor poses in convertible Bentley before stopping off in tattoo shop as UFC star enjoys life in California
Ronda Rousey's fight with Holly Holm moved forward to November at UFC 193 at Melbourne's 55,000-seat Etihad Stadium
Floyd Mayweather and Ronda Rousey feud rages on as boxer challenges UFC star: 'Let's see how much money you got!'
Max Holloway earns seventh consecutive win as early injury forces Charles Oliveira out of UFC Saskatoon main event
UFC featherweight prospects Max Holloway and Charles Oliveira to determine the future of the division in Saskatoon
UFC icon Ronda Rousey is a man among women... she is a super freak and super athlete, claims WWE star Brock Lesnar
UFC star Paige VanZant chills out with Cryotherapy session ahead of upcoming fight with Alex Chambers
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STARS OF SPORT
- MailOnline Fantasy Football is back... and you can pick Euro stars like Cristiano Ronaldo and Lionel Messi to boost your Premier League side
- As he returns to Southampton, how did Morgan Schneiderlin learn English? The Manchester United man watched Only Fools and Horses
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- Rugby World Cup gets underway Breaking new ground was the theme and England know that could be the upshot for the sport in this country
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What does it take to win a World Cup?
SPONSORED Power was the buzzword in England's 2003 win - and for South Africa and New Zealand also - Neymar poses with Star Wars actor John Boyega Barcelona superstar takes on British actor and Jedi warrior in celebrity poker match
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- Haskell bares all as England World Cup star poses naked ahead He is willing to lay his body on the line for the next six weeks and James Haskell isn't shy
- Murray thrashes Kokkinakis to put Great Britain ahead in Davis Cup semi-final But Australia drew level thanks to Bernard Tomic's win
- Everything you wanted to know about England Who runs the fastest 100m? And who likes to belt out Celine Dion? WILL KELLEHER guides you through the XV
- De Bruyne thanks fans for 'warm welcome' The £52m man was the centre of attention at a meet and greet and praised the City faithful after Manchester move
- Alli and Son seize chance to impress Harry Kane used the Europa League to become a regular. Dele Alli knows that, and didn't disappoint
- Man City's new green third kit unveiled by Nike... and it was inspired by the historic 1999-00 play-off comeback against Gillingham at Wembley
- The kids are alright Brendan Rodgers hailed the impact of Liverpool's young players as his side began their Europa League campaign with a draw in Bordeaux
- Ranieri promises to take his Leicester City players out for pizza if they keep their first clean sheet of season Leicester are riding high in the Premier League
- Robshaw is dating a singer, while Carter is wed to an ex-hockey star... meet the WAGs ahead of the World Cup Rugby World Cup takes over for next six weeks
- Hulk feels the effects of Champions League win with FOUR ice packs strapped to his legs Hulk powered through 90 minutes to help Zenit St Petersburg win
- Florenzi has Puskas Award in his pocket Forget Lionel Messi and Neymar. Alessandro Florenzi will steal the headlines with a magical long-range screamer
- France coach picks up Croydon parking ticket as things go from bad to worse for Les Bleus The bus pulled up in a south London bus stop on Wednesday night
- Joshua revving up for glory as British boxing's rising star treats himself to 'new toy'... a lime green dirt-bike Anthony Joshua is raising the (handle)bar
- Manchester United squad arrive back in England without Shaw after defender suffers broken leg in PSV defeat It was a solemn return to England for United
- Dawson sparks outrage in New Zealand by mocking haka with 'hakarena' dance Heightened tensions between World Cup hosts and favourites
- Forest release trailer for new film 'I Believe in Miracles', celebrating Clough's success The movie premieres at Nottingham Forest's City Ground on October 11
- Twitter mocks Ramos for dive during easy win over Shakhtar Real Madrid ran riot, but Sergio Ramos' ludicrous dive caught the eye of internet wags also
- Neymar looking to put his rivals in the shade(s) Brazil and Barcelona attacker agrees a big-money deal to be the face of Police Eyewear for third successive year
- The Great Britannia Bake-off: Bojan is cream of the crop as he wins Stoke cake-making competition Star forward is a man of hidden talents
- Rousey thrills Aussie UFC crowd ahead of her 'biggest challenge' against boxing world champion Holly Holm Vocal crowd was cheering her on
- Rooney uses injury time out to see Amir Khan's gym Paid a visit to Liverpool boxing's famous Smith brothers - Callum, Liam and Stephen
- Is that the way to World Cup glory? England put final preparations in place ahead of big opener Huge test ahead, but the players looked relaxed
- Neymar and Barcelona touch down in Italy for Euro opener with Roma Neymar and his Barcelona team-mates touched down in Italy for their game with Roma
- Berahino puts transfer saga behind him as wantaway star poses for West Brom portrait Berahino tried to force a move away from West Brom this summer
- Bellew stars in new film 'Creed' with Stallone back as Rocky Balboa Tony Bellew is to make his Hollywood debut alongside Sylvester Stallone in this new film
- Passing on knowledge: Henry takes charge of Arsenal U19s training Arsenal legend Thierry Henry led a training session alongside youth coach Ryan Garry
- US Open champion Djokovic admits to being inspired by blockbuster movie 300 Novak Djokovic summoned some cinematic inspiration
- New boy Martial heads for popular spot Wings with wife Samantha £58m new boy Anthony Martial has continued to settle into Manchester life with a trip to Wings
- West Ham 'Boys of 86' prove to be lucky charms as they attend win over Newcastle The 'Boys of 86' watched Slaven Bilic's side ease to a 2-0 home victory
- Murray takes on Celtic in a game of crossbar challenge... but how did the tennis star get on? Andy Murray and his team-mates swapped tennis for football
- What's on the menu, Gareth? Bale enjoys lunch with girlfriend Gareth Bale was spotted leaving a restaurant after lunch with girlfriend Emma Rhys-Jones
- Boxer Khan shows off 'King Khan' edition white Range Rover British boxer Amir Khan's special edition Range Rover was in full view in Manchester
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Sealed with a kiss: Djokovic celebrates his 10th slam success with wife JelenaNovak Djokovic beat Roger Federer to win the US Open on Sunday
- STEVEN GERRARD: 'Balotelli said: "I don't mark corners... I can't!" It was hard to manage mad Mario, but he made me smile. That wasn't the case with Diouf.'
- May and Corbisiero create their own Zizzi pizzas to raise money for Cancer Research UK The country's appetite for rugby has grown, and it's spreading to the players
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Van Gaal arrives at favourite restaurant Wings in chauffeur-driven Bentley
The car even had a personalised number plate for Louis van Gaal
- Gayle introduces fans to strip club, mirrored ceiling and 'Hanky Panky' bed in his house The batsman showed off some revealing pictures of his house...
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Beckham and DiCaprio lead star-studded cast for US Open final
The crowd included David Beckham and actors Bradley Cooper and Hugh Jackman - Bit slippy lads? Brazilian tie not called off despite ludicrously waterlogged pitch Watch the players in this Brasileiro Serie B match try to run with the ball...
- Nolan admits he was 'very miserable' towards end of time... as he trains with Orient while weighing up move Kevin Nolan needs a club
- Hamilton swoops into the front row of again... at Alexander Wang NY Fashion Week show Lewis Hamilton joined the Weeknd for a front row seat
- United striker Martial visits Wetherspoons for bargain meal as he gets used to Manchester Anthony Martial might be expensive, but his choice of dining certainly isn't!
- Ouch! Dyer puts his neck on the line to head home debut goal... as Leicester come from TWO goals down to win feisty Midlands derby Nathan Dyer was brave
- The transfer window's closed... but West Ham complete deal for Serbia U19 striker Belic West Ham have signed striker Luka Belic from OFK Beograd
- Get the beers in, Fergie! Sir Alex enjoys a pint on his return to Old Trafford (not that one!) Sir Alex Ferguson spent a day out at the cricket for England vs Australia
- STEVEN GERRARD: 'Some of the players came to me to complain that they had to walk 50 yards for a massage' EXCLUSIVE: Gerrard on the 2010 World Cup
- Arsenal duo Oxlade-Chamberlain and Chambers celebrate win at Joshua fight Anthony Joshua has gained many fans, including Arsenal stars
- Uh oh! Aguero injury scare for Manchester City after late win... but striker says on Twitter it 'doesn't seem serious' Sergio Aguero was forced off on Saturday
- The dynamic duo! Messi and Neymar to the rescue for Barca after Torres opener Lionel Messi scored the winner for Barcelona against Atletico Madrid
- STEVEN GERRARD: The truth about my United stamp fury EXCLUSIVE: He reveals the truth about last season's brutal stamp on Ander Herrera
- New Zealand touch down and head straight to see the sights The All Blacks arrived and their first stop was a welcoming ceremony at the Tower of London
- Serena is slammed MIKE DICKSON: We came expecting to see preparations for the coronation of Serena Williams, and instead got a sensational upset
- Sakho and Kouyate make two West Ham fans very happy... Diafra Sakho and Cheikhou Kouyate put a smile on fans' faces in South Africa