When Dai Shi beat up the Rangers profusely in a big showdown and sequestered R.J., the Rangers were left Master-less. R.J. told them they knew what to do, which was to go back to basics, which led them back to the Pai Zhuq Academy room where Dai Shi was kept. The Rangers noticed the masters' animal spirits etched in the wall and wondered where the gorilla, penguin, and antelope masters. They were greeted once more by their fallen teacher Master Mao. He sent them to the Spirit World at Casey's urging to be trained by three fallen masters. They put them through tests, Master Rilla sent Casey to a dimension that resembled his old bedroom and had to face his childhood fear of a monster in his closet. Once he got it over it, he opened the door to find he had passed the test and granted the Claw Boosters, Jungle Master mode, and Gorilla animal spirit zord.
He was later able to summon the Shark Spirit Ranger whenever needed. Casey's tiger spirit was stolen by Whiger and he was unable to morph, because if he did, his life would be in danger. Casey was teaching a class of young students at the time and one of his students that was always being picked on, helped in giving more power against a foe. Whiger's Rinzin was taken by Dai Shi and banished for not defeating Casey. Casey help and befriended the weakened Whiger and Whiger assisted him in saving his friends. Whiger then faded away because his power was running out, but he didn't leave Casey's mind. When Casey battled Master Finn in a test for his Master Stripes, he didn't know what to do and followed what the others did and failed. He then saw Jarrod save Camille from danger and was convinced that Jarrod was still in Dai Shi, but no one else believed him. He fought Dai Shi in his palace and came back with Jarrod and Camille to join in battle, for this he earned his stripes. After the finale battle against Dai Shi, Casey was teaching a class in Phi Zhuq with Jarrod and Camille as students.