Chael Sonnen explains why Arman Tsarukyan is the "hardest" fight for UFC lightweight champ Justin Gaethje

Arman Tsarukyan is believed to be on the cusp of a UFC lightweight title shot. Among the many prominent MMA personalities supporting the calls for Tsarukyan to receive a chance to compete for UFC gold is former UFC fighter Chael Sonnen. 

Arman Tsarukyan and Ilia Topuria are the frontrunners to fight Justin Gaethje for UFC lightweight gold

The consensus is that the UFC is likely to accord either Arman Tsarukyan or former two-division champion Ilia Topuria the next crack at the lightweight belt currently held by Justin Gaethje. The two-man race to face Gaethje for the title has been heating up as of late. 

Topuria hasn't fought since he dropped the lightweight belt in a TKO loss to Gaethje in June. Meanwhile, Tsarukyan has competed once this year, knocking out Mauricio Ruffy at UFC 331 earlier this month. "The Batman" is also booked to feature in a freestyle wrestling match for the RAF middleweight crossover belt. He'll take on Dillon Danis for it in the main event of RAF 14 on October 23. 

Chael Sonnen lauds Arman Tsarukyan, explains why he's the toughest challenge for Justin Gaethje

Taking to his official YouTube channel, ex-UFC star Chael Sonnen alluded to the fact that the veteran Justin Gaethje has faced almost all the elite fighters in the current UFC lightweight crop. 

On that note, he underscored that "The Highlight" hasn't fought Arman Tsarukyan as of yet. The fighter-turned-analyst explained that it's this very element -- that of Tsarukyan being unknown to Gaethje -- which currently makes him the biggest threat to the champion. 

Sonnen stated, "The hardest guy in that weight (lightweight), I believe, would be Arman (Tsarukyan), but not only because of Tsarukyan's skills, but because of the unknown."

Moreover, Sonnen made an allusion to Gaethje's recent assertions. For context, the lightweight titlist had implied that he'd either retire or face Tsarukyan, who many feel is the true number-one contender right now. He's also highlighted that Tsarukyan's case for a title shot is stronger than Ilia Topuria, whom he (Gaethje) isn't interested in rematching anytime soon. 

Speaking of which, Sonnen said, "So for Gaethje to take the stance of bring me something new. A lot of guys have said things like that, but that was to avoid a hard fight. In Gaethje's case, that is then to invite a hard fight." 

Watch Chael Sonnen address the Arman Tsarukyan threat looming large over Justin Gaethje's UFC lightweight reign below (*comments at the 3:40-minute mark of the video):