On the heels of the Apparatus waking up and promoting J.D. Martinez, let's take a look at a few of the A/A+ players who may be candidates for a promotion, and give a verdict.
Lancaster JetHawks Pitching - 22.9 5.13 ERA/1.44 WHIP)
Cartwright won't be 23 until the end of October, but he's hitting .304/.364/.528 for Lancaster with 43 extra-base hits (24 doubles, 9 triples, 10 homers). He's getting pretty lucky, with a .368 BABIP, and his Home/Road splits are skewed: At home, he's hitting .353/.412/.612 with a .398 BABIP. On the road, he's hitting .250/.311/.434, with an overall 49.8% groundball rate, 35.1% flyball rate, and 14.3% line drive rate.
Verdict: Play it out in California.
The California League is quite obviously a hitter's league, so when a pitcher dominates, it's really encouraging. For instance: LHP Dallas Keuchel. Keuchel is 22, almost a full year younger than his Cal League counterparts. Yet Keuchel is leading the rotation with a 3.30 ERA (team average is 5.28) and a 1.27 WHIP. His FIP is 4.23, and he's still been a touch unlucky with a .307 BABIP. He gets a ton of groundballs (62.2%, compared to 22.4% flyballs). Eight of the ten home runs he's allowed have come at home, and he's got a .348 home BABIP. And he's thrown eight straight quality starts, dating back to May 28.
Verdict: Bring him up!
League Average: 21.8 years old, 3.79 ERA/1.31 WHIP, 2.61 K:BB ratio
The SAL average age for batters is 21.5 years old, with a .702 OPS (.256/.323/.379). Yet Jose Altuve is 20, with a .301/.355/.439 slash line - 91 points over league average in OPS. He has only struck out in 12.2% of his plate appearances, and while his 27 walks come out to only 7.2% of his plate appearances, he's now leading the team in batting average. He's consistent, too, hitting LHP for an .816 OPS and RHP for a .789 OPS. At home his OPS is .818, compared to .775 on the road. If Altuve doesn't get called up, it won't be an egregious error, as he's younger than his competition by about a year and a half, but we should be keeping an eye on him.
Verdict: Play it out in the SAL.
The SAL average age for a pitcher is 21.8 years old, and Leon will be 24 in September. In 55.2IP, Leon has posted a 2.33 ERA/1.17 WHIP, below the league average of 3.79 ERA/1.31 WHIP. He also is posting 9.7 strikeouts per nine innings, and it's not a matter of luck, either. His FIP is 2.77, and his BABIP is .284. Right-handed batters are hitting .152 against him, and he's striking them out to the tune of 45K:14BB. His groundball rate (58.8%) is well-suited to Lancaster, as well.
Verdict: Bring him up!