http://www.whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx?pid=2609249
I got screwed with a terrible AAA hitting coach in the last cycle of coach hiring in S11. Coaches hitting IQ was 44 and the 2nd lowest 67. For S12 he was in the majors with a hitting coach that had a hitting IQ of 91 (tied for 2nd best in world)
S11 - AAA at age 21 in 3rd pro year he grew: 0 contact, 0 vsL, 1 vsR, 1 eye
S12 - ML at age 22 in 4th pro year he grew: 2 contact, 2 vsL, 4 vsR, 1 eye
Kinda an extreme example since the S11 coach was soo bad, but it at very least hilights that poor coaching can certainly stunt growth.