Conor McGregor
Conor McGregor suffered his first UFC defeat in March after stepping up two divisions to fight Nate DiazRey Del Rio/Getty Images

MMA star Conor McGregor has added considerable weight to speculation that he is set to meet Floyd Mayweather Jr in a lucrative boxing bout in Las Vegas this summer. The 27-year-old, currently the UFC's featherweight champion and biggest draw, was initially due to headline UFC 200 in two months' time and face Nate Diaz in an attempt to avenge his welterweight submission defeat suffered in March.

However, a failure to fulfill his promotional obligations led to McGregor being bumped from the card and he strongly hinted at an early retirement last month, before later clarifying that he had not given up the sport. His hopes of still topping the bill at the T-Mobile Arena were dealt a final blow with the announcement that Daniel Cormier's lightweight grudge match against Jon Jones would take centre stage, and The Sun subsequently reported last week that he was on the verge of agreeing to a historic fight with Mayweather that would see him net approximately £7m ($10.1m).

Although it was claimed that an announcement was expected in the coming weeks with only the finer details of the purse and contracts to be ironed out, most fight fans remained sceptical that such a bout would actually come to fruition. However, Mayweather's father has appeared to suggest that the fight is happening and the brash Dubliner has now taken to Twitter to post a mock-up staredown between him and "Money" accompanied by a caption that simply reads "MMA vs Boxing".

Mayweather retired from boxing after a comfortable victory over Andre Berto in September 2015, calling time on an illustrious career that had seen him amass an unbeaten 49-0 record and win 12 world titles in five different weight divisions en route to being labelled as the most accomplished fighter of his generation. Although he appears happy in his new role as a promoter, last week he admitted that he could return to the ring for a nine-figure payday. Rumours suggest that a meeting with McGregor is likely to net him in excess of $100m.

Responding to that speculation on Saturday (7 May), Mayweather told FightHype.com: "It's possible. It was a name that was shot at me. The rumours that you've been hearing is the rumours that I started. It may not be a rumour. Keep your fingers crossed and maybe a boxer versus an MMA fighter… we just don't know."

McGregor was asked about the possibility of fighting Mayweather before his defeat to Diaz, claiming he was open to discussion but insisting that he "holds the key to the fight game". He had previously responded angrily to the former pound-for-pound king's suggestion that racism may play a part in the praise of the Irishman's trademark trash-talking approach in comparison to the condemnation of his own.

"Floyd Mayweather, don't ever bring race into my success again," he wrote on Facebook. "I am an Irishman. My people have been oppressed our entire existence. And still very much are. I understand the feeling of prejudice. It is a feeling that is deep in my blood.

"In my family's long history of warfare there was a time where just having the name 'McGregor' was punishable by death. Do not ever put me in a bracket like this again. If you want we can organise a fight no problem. I will give you a fair 80/20 purse split in my favour [seeing] as your last fight bombed at every area of revenue. At 27 years of age, I now hold the key to this game. The game answers to me now."

Twitter/@TheNotoriousMMA