Sin Cara was let released from his contract last month and the WWE has been using Hunico under the mask portraying Sin Cara since they let the original go. According to PEW on April 8, Rey Mysterio explains the reason Sin Cara was fired was because of poor work ethic.
According to Mysterio, it is sad because he really felt that Sin Cara was the man who could have replaced him as the Latino face of the WWE. However, Mysterio said that things didn't work out because Sin Cara did not work hard enough to adapt to the WWE style of wrestling. He also said that Sin Cara wouldn't bother with learning English.
Rey Mysterio hinted that if Sin Cara had tried harder in those two areas, the end result could have been different for him in the WWE.
This comes as no surprise, because Sin Cara said before that he had no desire to learn English. According to Sin Cara, he didn't want to learn English because he doesn't like the language enough to care about learning it. He went on to say that when he wrestled in Japan, he learned the language because it is a better language.
With statements like that, as well as the numerous botched spots in matches he participated in, Sin Cara went from being an exciting prospect to someone the WWE chose to cut. However, since Sin Cara is a huge merchandise seller, they just repackaged Hunico under the Sin Cara mask and have been using him ever since, including in the "Wrestlemania 30" battle royal.