It's difficult enough to conquer one opponent inside an MMA cage, but Alex Pereira will have two obstacles to overcome in his attempt to regain the UFC light heavyweight championship on Saturday at UFC 320 (ESPN PPV, 10 p.m. ET).

His primary focus, of course, will be on champion Magomed Ankalaev , who dethroned Pereira when they met in March . The other stumbling block Pereira will be up against is UFC championship history.

Ankalaev-Pereira 2 will be the first bout for both fighters since the belt changed hands, and toppled UFC champions have not fared well in immediate rematches. In the 16 such matchups in the fight promotion's modern era (since November 2000, when the UFC first utilized the Unified Rules of mixed martial arts), four ex-champions have succeeded in regaining the ti

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