When it comes to the commercial side of mixed martial arts, no one comes close to Conor McGregor. The UFC's golden goose has headlined most of the highest-selling pay-per-views in promotional history and takes immense pride in being the sport's biggest superstar.McGregor recently commented on a potential superfight between the UFC's current featherweight and lightweight champions. Islam Makhachev claimed the 155-pound strap this past weekend in Abu Dhabi and subsequently called out reigning 145-pound titleholder Alexander Volkanovski for his first title defense.Makhachev called for the champion versus champion bout to take place in Australia next year, with his lightweight title and Volkanovski's status as the No.1 pound-for-pound fighter in the world up for grabs.Chamatkar Sandhu@SandhuMMAIslam Makhachev and Alexander Volkanovski just agreed to a fight in Australia! Lightweight title on the line. Pound for Pound bragging rights on the line. BRING IT ON! #UFC2801233184Islam Makhachev and Alexander Volkanovski just agreed to a fight in Australia! Lightweight title on the line. Pound for Pound bragging rights on the line. BRING IT ON! 🏆 #UFC280https://t.co/YabyOJDqZeConor McGregor took to Twitter to disparage Volkanovski and Makhachev's ability to sell pay-per-views. He posted an image of both champions and captioned the post:"My two old belts. On two little ticks. This fight does 10 buys."Conor McGregor@TheNotoriousMMAMy two old belts. On two little ticks. This fight does 10 buys220651235My two old belts. On two little ticks. This fight does 10 buys https://t.co/8AIzVyxQUlOnce a two-division simultaneous titleholder, Conor McGregor is currently recovering from a broken leg injury that he suffered in his rubber match against Dustin Poirier at UFC 264 last year. He is expected to return to action next year.The Irishman notably occupies all five spots on the premier MMA organization's top-five pay-per-view list. His blockbuster grudge match against Khabib Nurmagomedov back in 2018 remains the highest-selling pay-per-view in UFC history, accruing 2.4 million buys.Coral@CoralMost UFC PPV buys: Khabib vs McGregor Diaz vs McGregor II Diaz vs McGregor I Alvarez vs McGregor/Lesnar vs Mir Aldo vs McGregorAbsolute box office.30767Most UFC PPV buys:1⃣ Khabib vs McGregor2⃣ Diaz vs McGregor II3⃣ Diaz vs McGregor I4⃣ Alvarez vs McGregor/Lesnar vs Mir5⃣ Aldo vs McGregorAbsolute box office. https://t.co/NaWb2bEa7GDana White confirms timeline for Conor McGregor's returnReports suggesting that Conor McGregor wasn't tested by USADA this year sparked outrage in the MMA community, with several fighters going as far as to claim that the Irishman might not be entirely clean.Aaron Bronsteter@aaronbronsteterAfter cross-referencing the entire active UFC roster with USADA's athlete test history database, I found that Conor McGregor was the lone active fighter, (aside from some athletes who signed after Aug. 1) to not be tested by USADA.tsn.ca/ufc-star-conor…1744216After cross-referencing the entire active UFC roster with USADA's athlete test history database, I found that Conor McGregor was the lone active fighter, (aside from some athletes who signed after Aug. 1) to not be tested by USADA.tsn.ca/ufc-star-conor…McGregor's team didn't comment on the matter, but UFC President Dana White may have perchance confirmed the news. During the UFC 280 post-fight press conference, MMA Junkie's Farah Hannoun asked White whether the Irishman is no longer in the USADA testing pool.If such is the case, McGregor will be required to fulfill six months of mandatory testing from USADA before competing inside the octagon again, which White confirmed at the UFC 280 post-fight presser.MMAFighting.com@MMAFightingDana White says Conor McGregor will need six months in the USADA testing pool before returning.48944Dana White says Conor McGregor will need six months in the USADA testing pool before returning. https://t.co/aLbbFiWnSE