By John Morgan, MMA Underground Gamrot calls for a fight with Justin Gaethje, “the most brutal guy in the division,” in his next bout. View the original article to see embedded media. LAS VEGAS—In a matchup featuring two of the UFC’s top lightweight prospects, Mateusz Gamrot earned an incredibly hard-fought decision in a 25-minute battle with Arman Tsarukyan. The contest served as the headlining matchup of Saturday’s UFC on ESPN 38, which took place at the UFC Apex. High-level grappling exchanges were on display from the start, with each looking for takedowns but finding capable defense from t…