not that an easy decision for me...
his vsR sits at 67, not that outstanding, everything else is pretty great though...3 pitches in the 80's
he's obviously still improving, under normal circumstances i would promote him next year...
the question that needs asked is how much better is he than your other options?
I did a player search in my league (Summer of 49) and at this moment he is very similar to this guy who plays in a neutral park
Louie Nerudahe has a career 1.36 WHIP, how much better is that than the guy whose innings he would be replacing?
looking at your starters it looks like he'd be replacing
Clark Speaker and kind of jump in as the 2 or 3 starter, speaker has a 1.49 WHIP and has been ok
by promoting him this year instead of waiting 21 games into next season you are fast tracking free agency by one year, his first year of arb would be year 10 instead of 11, and his first expensive year of arb would be year 11 instead of 12, you'll pay about 8 million more over those 2 years with everything else being pretty much a wash
Think of it this way, by promoting him early you will pay 8-10 million more for him over his career if he stays with your franchise or if he leaves at some point you will lose him a year earlier...is the remainder of this season worth 8 to 10 million to you (a shortened season before he reaches his prime) or if he leaves via free agency down the line there is the chance of losing a year of his service (in his prime no less.)
far from an easy decision this is a very complicated, nuanced decision...
my guess is adding him to your team will add 1 or 2 wins to the bottom line, may be the difference between the playoffs or not, or it may make no difference...doesn't seem worth 8 to 10 million dollars of your payroll spread out over seasons 10 and 11 (i'm assuming you'll stick with this loaded team, if not the whole point is moot)