Conor McGregor slammed the UFC for holding him back from fighting in the octagon as the former champion switches to boxing and prepares for a showdown with Manny Pacquiao.

McGregor and boxing legend Pacquiao are set to go head-to-head in the ring in 2021 – a huge portion of the earnings to be donated to those affected by the coronavirus pandemic, the latter's aide Jayke Joson said on Saturday.

Irishman McGregor announced his decision to retire in June, having returned to the UFC in January after a 15-month absence and knocked out Donald Cerrone at welterweight in just 40 seconds.

McGregor has not fought since – the former featherweight and lightweight champion had been planning to fight three times in 2020, but the COVID-19 crisis scuppered that strategy.

UFC president Dana White has previously hinted at a possible comeback next year after revealing he is working on some "fun stuff" for McGregor, however, the 32-year-old hit out via Instagram.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

A post shared by Conor McGregor Official (@thenotoriousmma) on

"The very first shot of the fight," McGregor wrote as he discussed his 2017 defeat to unbeaten boxer Floyd Mayweather Jr. "Right on the button through the guard. I didn't even put anything into that shot. Just placed it. It was hard for me not to dwell on the full 12 rounds that were potentially ahead of me and hold back my shots early.

"Still tho [sic] right on the absolute button. The first punch thrown. Remember the experts saying I wouldn't land even one lol. I landed more than them all. The picture above is the very first punch of the fight thrown, and landed, and inside the very first second of the fight. Bums all of them 'experts'. Listen to none of them! Really I should have just sat right thru that shot and took his head off and f*** the distance. If it didn't work out just give him a good boot into the neck and get DQ'd [disqualified] and fined and who'd give a f***. I'm upset I fully followed the rules for that fight to be honest. Floyd deserved a volley at the least. A shoulder even, break the face.

"Manny not so much tho [sic] I don't think, but I will see how the build-up goes and wait to hear what bitter old Freddie Roach has to say and then make a decision. My Whiskeys at half a b and climbing I could take a fine. I'd rather fight MMA anyway not sure why I've been held back like this, it's borderline criminal at this stage.

"The biggest number generator in the game asking for four fights since February this year and getting left on seen. It's pretty f***** up when I keep thinking of it. I've been right here this whole time. Bob Chapek, do you copy! I repeat, Bob Chapek - Do You Copy!

"Anyways boxing it is for now and I'm up for this! I hope no bottling takes place here. I'm already agreeing to these limited rules and holding back my full array of weapons. Let's get it going guys. Much love, the champ champ."