Tony Cingrani has only been in professional baseball for a little over two years. And when you consider that he spent 2011 with the short-season Billings Mustangs, he's really only been around the equivalent of a full season and change. So the whole question of whether or not he's arrived would seem entirely premature - that is, if he hadn't been dominant at every level he's blown through, up to and including his performance against a playoff-caliber major league team last week.
While Cingrani has been fooling hitters from Bakersfield to DC, he's also been chased around by nagging doubts about his ability to be a starter over the long term. For what doubters remain, this has to do less with his performance than the implication that a fastball-dependent pitcher who isn't also a power pitcher is a suspicious breed.
Cingrani has thown 82% fastballs so far in his major league career, mixing in a changeup and a breaking ball (what you might call a "slurve"). As Cy Schourek already pointed out, this is much less a problem than it would seem once you look around the league.
Cingrani's most recent counterpart, Ross Detwiler, was a fellow lefty and one of a number of starting pitchers who have been throwing fastballs more often than Tony this season. Detwiler is going to his around 90% of the time, while he was closer to 80% last season. Meanwhile, he's kept an ERA in the 3.00s since 2011.
Coming from the left side, Detwiler and Cingrani both have the jump on lefty mashers like Harper or Choo. And they both can locate the fastball well without nibbling around the plate.
But Cingrani does some things Detwiler can't. His wind-up, which has been well documented, is quirky enough to generate whiffs on its own. Cingrani can also touch 96-97 on the gun, while sitting comfortably at 92. It may not be long before NL hitters start figure out Cingraii's trebuchet delivery, but it's hard to hit what you can't time. Most hitters would admit it's difficult enough to time a well-located fastball with reasonable zip. Tony chucks one that goes in and out of view several times and leaves his grasp about as late as possible.
In light of all that, I think Cingrani has asked and answered this fastball business for now.
The other thing that gives me some confidence in Cingrani is what distinguishes him from other Reds' pitching prospects who have torn up the minors. Looking at the post-steroid era as the cut-off - let's say 2007 and onward - the following starters have wound up in the Baseball America Top 10 Reds prospect lists and had a chance to get to the majors. I'll throw Zach Stewart in, even though he just missed the cut:
Cingrani has a better walk-rate (2.8 BB/9) and strikeout rate (11.8 K/9) in the minors than virtually every pitcher on that list, though Cueto's control was better. The big caveat is that Cingrani was older than Cueto, Bailey and Wood at most levels. But I think the point stands: that kind of singular dominance puts you in rare company.
If Tony is able to maintain anything close to the level of fastball command, general control and bat-avoidance he has as a 23-year old in the majors, things look good.
To that point, here's a list of lefty starters 27-or-younger who were able to put up at least a partial season close to Cingrani numbers:
(Single seasons, From 1901 to 2013, Younger than 27, Throws LH, (requiring SOp9>=10, At least 75% games started and At least 50 Innings Pitched), sorted by greatest Adjusted ERA)
Even Perez and Kazmir had several very good seasons as starters, which is more than a lot of scouts were willing to allow Cingrani less than a year a go.
I guess my point is: