don't worry- he may not be the guy that can line up complete games or may not be able to throw 98 mph anymore but HE STILL HAS THE BEST STUFF IN THE MAJORS
he doesn't have the huge frame that is necessary to be a strikeout pitcher in the majors late into one's career. so the only thing for him to do his gradually modify pitching style so as to not to try to K every batter. you look at his career path closely thats exactly whats hes been doing, so he should be fine.
and finally even though im not too happy to day this but-
theres a possibility that he might take to closing later in his career if he has too many endurance issues