2011 B.A.A. 10K champions Geoffrey Mutai and Caroline Kilel have returned to Boston with their eyes on Sunday's second annual B.A.A. 10K, ready to take to the roads of Boston's Back Bay in hopes of defending their titles from a year ago. Mutai, the 2011 Boston Marathon men's champion, and Kilel, the 2011 women's champion, are eager and ready for Sunday's race, seeking to add another chapter to their already excellent tradition of racing in Boston.