Former two-division UFC World Champion, Conor McGregor recently ripped into Bellator MMA for not having a performance-enhancing drug-testing system in place. The Irishman even went ahead and reminded Scott Coker's promotion that it is high-time Bellator starts following the footsteps of the UFC and tests their fighters more effectively.Conor McGregor's tweet caught the attention of former UFC Heavyweight Champion, Fabricio Werdum, who responded by labeling the former as a "loser" and assuming that his tweet was a jab towards Bellator Champion, Cris Cyborg.The Notorious One cleared the air in response by stating that his tweet was not meant for Cyborg but was rather a request to Bellator as an entire promotion.Huh? I did not mention Cris whatsoever. Nothing to do with Cris at all. It is a request to the promotion, as a top tier one, to up its PED testing program. As currently there is zero in place. This is a dangerous business and to take a lax stance here, at this level, is wrong.— Conor McGregor (@TheNotoriousMMA) October 24, 2020However, this wasn't the only response Conor McGregor had in store. The former UFC Lightweight Champion soon questioned Fabricio Werdum for being banned for steroid usage and potentially signing with Bellator.McGregor's follow-up tweet can be found at this link (contains strong language)Werdum then referenced Sinead Kavanagh - Conor McGregor's teammate - and claimed that her initial tweet about Bellator needing to drug test its athletes was aimed at Cris Cyborg.Conor, however, denied the former UFC heavyweight champion's accusation and stated that while Kavanagh is his teammate, Cyborg is managed by the Paradigm Sports - the same agency that manages the Irishman.They never fought. I train Sinead. I manage Cris. Both tremendously gifted warriors. This is not about either! Or any of the roster for that matter. It is about the promotion itself stepping up to the plate, as one of the top tier organisations in MMA, and upping its testing.— Conor McGregor (@TheNotoriousMMA) October 24, 2020However, Werdum went after McGregor one final time, referencing his extra-curricular life.An alcoholic and a Coke head should not worry about testing anything @ScottCoker always do a good job— Fabricio Werdum (@FabricioWerdum) October 24, 2020What's next for Conor McGregor in the UFC?Conor McGregor is reportedly set for his Octagon return in early 2021 in a rematch against Dustin Poirier. However, nothing has been officially confirmed, as of now. McGregor's return to the Octagon is likely to be followed up by his return to the boxing ring for a clash against Manny Pacquiao.On the other hand, Fabricio Werdum recently competed in his last fight for the promotion when he defeated Alexander Gustafsson. Werdum's next fight in the MMA is yet to be announced but it is likely to take place under the Bellator banner.