Conor McGregor has once again fuelled the growing speculation over a showdown with Floyd Mayweather, dropping footage of himself in a heavy sparring session inside the boxing ring.

Both McGregor and Mayweather continue to tease the possibility of the cross-sport spectacle that could one day become the richest fight in combat sport history. While the Mayweather camp not too long ago described McGregor's efforts to push for the fight as a "con job" to "keep his name alive", the undefeated American now insists taking on the UFC superstar is the only fight that could possibly tempt him out of retirement.

The five-weight world champion called time on his boxing career in September 2015 after victory No 49 over Andre Berto with the list of men to land a telling punch on him during his time at the top a tellingly short one.

McGregor, whose last win in the octagon came via a devastating four-punch combo, believes he has the tools to end that undefeated streak.

"I've got the reach. I've got the youth. I've got the confidence. I've got the unpredictable style. You can't prepare for a style like me."

And in his latest Instagram video, the 28-year-old can be seen furiously sparring at Dublin's SBG Ireland as the hype continues to build.

Boxing at SBG

A video posted by Conor McGregor Official (@thenotoriousmma) on

McGregor, who became the UFC's first ever double champion last November, is currently taking a break from competition ahead of the birth of his first child but his name continues to dominate.

At a recent Q&A session in Manchester, the Dubliner was quizzed on a possible switch to WWE, his own McGregor Promotions and a possible third fight with Nate Diaz. But inevitably, it was his comments on Mayweather which rose to the top.

"100%," McGregor said when asked if Mayweather will be his next fight. "I believe the next time I step into a combat arena will be through the ropes wearing 10-ounce or eight-ounce gloves. I believe so."

A week later, Mayweather upped the ante. "Most likely the fight between me and Conor McGregor will happen," Mayweather told Sky Sports while in attendance at the WBA welterweight title match between Carl Frampton and Leo Santa Cruz in January.

"That's the only fight that will get me back in the ring. He's going to do a job on his side and we are going to do a job on my side and hopefully all the fans in the UK come over and support me.

"I don't know (when it will be), I need to communicate with my team, the fight hasn't been made yet, but it is all about entertainment so hopefully we can make it happen."