McClure, hired after the 2011 as a scout and roaming pitching instructor, was promoted to the position of pitching coach after Bobby Valentine was brought on as manager. So far, his tenure has seen the worst results from a rotation since 2006, with marked declines from Josh Beckett and Jon Lester.
It's difficult to parse out in any given situation what fault lies at the feet of the coach compared to the pitchers--especially from outside of the organization--but McClure has had few successes throughout. Felix Doubront has faded with time, though that may simply be due to his inexperience with such a high innings count. Daniel Bard was, of course, an unmitigated disaster. All the good that's come from Clay Buchholz of late is still not enough to get his ERA under 4.00 after his extended run of terrible pitching early, and as decent as the bullpen has seemed, many of the top performers have come from the minor leagues or outside the team while players who were here all along--Vicente Padilla, Alfredo Aceves, and Mark Melancon, for instance--have been largely disappointing.
This makes three pitching coaches for Boston since John Farrell left to become the manager of the Toronto Blue Jays.