Conor McGregor has taken aim at Justin Gaethje for the second time in a week, after the American played down McGregor’s callout in the wake of UFC 291. Gaethje knocked out Dustin Poirier in the second round on Saturday, avenging a 2018 loss to his compatriot and winning the ‘Baddest Motherf*****’ title. McGregor was apparently unimpressed, however, tweeting after the lightweight fight: “Justin, I’ll slap you around. I KO him one shot. Guarantee it.” Gaethje, 34, dismissed the former dual-weight champion’s callout, referencing the fact that McGregor is currently absent from the United States Anti-Doping Agency (Usada) testing pool. Athletes must be in the pool for six months and return two negative results – and zero positives – in order to fight in the UFC. Although McGregor, 35, has never failed a drug test, Gaethje said: “I’m not going to fight someone on steroids [...] I don’t want to fight someone that’s cheating [...] I think he’s turned me down six times. And usually you have to lose to fight him, so don’t know what’s going on.” McGregor has now hit back, tweeting on Tuesday (1 August): “This guy is about as smart as two planks. “He is a one shotter for me. I snipe him dead in one single shot. And easily.” McGregor has not fought in two years, since suffering a broken leg in his second straight loss to Poirier. The Irishman is set to face Michael Chandler next, but no date, location or weight class has been announced for that bout, with McGregor’s absence from the Usada pool proving problematic. Meanwhile, Gaethje has won two fights in a row since suffering a submission loss to Charles Oliveira in May 2022. The American outpointed Rafael Fiziev in March before knocking out Poirier at UFC 291. Gaethje may yet challenge for the UFC lightweight title – for the third time – in his next fight. Champion Islam Makhachev is scheduled to defend the belt against ex-champion Oliveira in October. Click here to subscribe to The Independent’s Sport YouTube channel for all the latest sports videos. Read More Justin Gaethje reacts to Conor McGregor callout after knocking out Dustin Poirier Justin Gaethje and Dustin Poirier share wholesome backstage moment after UFC 291 KO Jake Paul vs Nate Diaz live stream: How to watch fight online and on TV this weekend