He needs to maintain his weight while doing extra trainings and sparrings, if he wanted to win over Martinez he needs to condition and make sure that he really prepared both physically and mentally, he's still young and if the goal is to win more titles or have a much better life like Pacquiao and Donaire, he needs to win this fight and reclaimed his belt.
Weight can only be maintain in diet, not doing extra training an sparring. On the contrary if might hurt him a bit if he go to far with it. His trainer should know when his boxer will hit his peak and enough to be 100% in the actual fight. Not being 100% prior to the fight because on the day itself he might lose some of his physically strength because he overtrain. At least that's why I heard from Roach before, when he trains Manny, they needed at least 8 weeks for fight preparation.
What I mean is while he's maintaining his weight with his diet, doing some extra and sparring to enhance his fighting skills may help him in winning this rematch, I remember the first fight where he got an issue with his weight might be possible that the camp focus in meeting the required weight and they've might lack of trainings and sparrings.
Though we never know if it's just an excuse or he really struggles but now that he's been grant for another try, he needed to bring everything here.
This fight will bring big impact in his future career, very important to keep his chance to make more money from this industry.