Verlander's first two MLB starts
11.3 IP 15 H 9 ER 5 BB 7 K 7.15 ERA 1.77 WHIP
Turner's first two MLB starts
9.6 IP 10 H 8 ER 3 BB 8 K 7.45 ERA 1.34 WHIP
Greg Maddux first five MLB starts
30.0 IP 43 H 18 ER 11 BB 19 SO 5.40 ERA 1.80 WHIP
Small sample sizes
Now Minor League Stats before age 23:
Verlander 0.90 WHIP 5.23 SO/BB 10.3 SO/G
Baugh 1.09 WHIP 4.31 SO/BB 9.7 SO/G
Turner 1.14 WHIP 3.66 SO/BB 7.7 SO/G
Porcello 1.19 WHIP 2.12 SO/BB 5.4 SO/G
A. Miller 1.19 WHIP 2.69 SO/BB 7.6 SO/G
Maddux 1.19 WHIP 2.06 SO/BB 5.7 SO/G
Wheatland 1.25 WHIP 3.32 SO/BB 8.1 SO/G
Gonzalez 1.26 WHIP 2.54 SO/BB 10.3 SO/G
Sleeth 1.39 WHIP 2.35 SO/BB 7.4 SO/G
Greisinger 1.45 WHIP 1.87 SO/BB 5.8 SO/G
Baugh, Wheatland and Sleeth, all, had arm troubles in the minors. It is more about bad luck, then not living up to prospect status.
Minor league stats for pitchers can be predictive. Most people understand WHIP (under 1.20 is preferred). SO/BB Ratio above 2.00 is good, but above 3.00 is preferred at the minor level. Anything above 4.00 is outstanding. Next, SO/G shows somewhat the quality of stuff. Anything above 7.0 is good, anything above 8.0 is outstanding.
So, if you evaluate pitchers with these in mind, Baugh and Wheatland projected to be a #1 or #2 (before they got hurt). Sleeth and Greisinger were reaches given their stats. Miller projected as a #3, but once he arrived, he inexplicably could not maintain control he had in the early minors.
Aside his SO/G ratio, Gio Gonzalez did not project above a #3 starter, which is about where he is at.
I showed Greg Maddux' career, only to offer hope for someone like Porcello. I am not saying Porcello will be the next Greg Maddux, but there are a quite few similarities in the minor and early MLB careers.