Didi Gregorius starting to ‘knock on the door’ of Yankees return

Running off the field after taking batting practice and fielding grounders prior to Sunday’s game, Didi Gregorius said he felt “good, really good” as he comes back from a bruised left heel that has sidelined him since Aug. 20. Aaron Boone doubted the shortstop would be ready for Monday’s game against the A’s in Oakland…