This spring, Greinke is lurching back toward "not good," and that's decidedly bad news for the Snakes.
It might even be a disaster.
Through 2.2 exhibition innings, Greinke has surrendered a .333 opponents' batting average. That's a tiny sample, obviously. More troublingly, Greinke's fastball has been sitting in the mid-80s and topping out at 87 mph, per Nick Piecoro of AZcentral.
In his most recent outing on Wednesday, he exited after an inning with groin tightness, per ESPN.com.
Diamondbacks fans have every right to be anxious. Greinke is, too.
"Every year, I get nervous that it's not working good enough and that it's not going to come fast enough," Greinke said, per Piecoro. "Same thing this year. I think it's going to be ready, but in the back of my mind I'm always a little nervous that it's not actually going to be there and be ready by the time the season starts."
Greinke battled diminished velocity last spring and went on to post a 3.20 ERA with 215 strikeouts in 202.1 innings. He made the National League All-Star team and finished fourth in NL Cy Young Award voting.
That said, the 34-year-old right-hander posted a 4.37 ERA in a mediocre 2016. His velocity, meanwhile, has been on a steady downward trajectory.
It didn't prevent Greinke from being an effective pitcher last year, but it's a disturbing trend.
Keep in mind, the Diamondbacks owe Greinke $138.5 million dollars through 2021. They went all-in when they signed him to a $206.5 million megadeal in December 2015. They need him to be an ace if they're going to get back to the postseason.
The Los Angeles Dodgers are the toast of the National League West. The Colorado Rockies, who snagged the NL's second wild-card slot last season, are right there. The San Francisco Giants are much improved after adding some quality veteran pieces.
The D-backs have other high-upside arms, including Robbie Ray, who posted a 2.81 ERA and paced the Senior Circuit with 12.1 strikeouts per nine innings last season. They also have an offense that finished fifth in the NL in runs and OPS, though they did lose slugger J.D. Martinez to free agency.
That gives them insurance, but it doesn't eliminate the need for an effective Greinke. Manager Tony Lovullo has yet to name an Opening Day starter, which tells you all you need to know. Lovullo said, per Piecoro:
"We need to probably cycle through some of the candidates and make sure they're healthy and strong and ready. I know from just listening to some of the comments, Zack is concerned about his velocity. There is a whole bunch of different things and moving parts to this equation. We're going to let everything kind of settle down, get some input from Zack, see where he's at."
As USA Today's Ted Berg recently opined: "Harboring any sort of self-doubt seems antithetical to playing professional baseball, a sport of minuscule margins dominated by randomness and failure. Most baseball players, even the lousy ones, practically ooze macho confidence."
In 2009, Greinke won his first Cy Young Award with K.C. He overcame whatever obstacles stood in his way. There is precedent for the four-time All-Star clearing hurdles, rediscovering his form and exceeding expectations. No one should be pressing the panic button in mid-March.
At the same time, there are no guarantees when it comes to pitchers entering their mid-30s. Was Greinke's resurgent 2017 a harbinger of things to come or an anomalous late-career blip?
If it was the former, the Diamondbacks will be in the thick of the NL playoff race once again. If it was the latter, they could tumble under the weight of an overpaid albatross.
We know what Greinke is when he's good. We know what he is when he's not good. Now, we wait to see what he'll be in 2018.