Each and every spring, fans and teams alike pay extra attention to the radar gun. With the new year underway everyone is anxious to see who has added velocity and -- probably more urgently -- who is missing velocity. Missing velocity is a pretty good indicator of age-related decline or injury.

Arizona Diamondbacks ace Zack Greinke took the mound in a minor league game Thursday morning, and his fastball was sitting mostly in the mid-80s, well below where it usually sits during the season.

Last season Greinke's heater averaged 91.0 mph in 2017, down from 92.3 mph in 2016 and 92.4 mph in 2015. Like most veteran pitchers, Greinke's velocity has gradually been trending down for years now, since peaking at 95.2 mph way back in 2007. He turned 34 in October and it is completely normal for a pitcher in his mid-30s to lose some velocity.

That said, dipping into the mid-80s is always a cause for concern, even in spring training. Greinke even admitted he always worries a bit when his velocity is down during the spring. From Nick Piecoro of the Arizona Republic:

"Every year, I get nervous that it's not working good enough and that it's not going to come fast enough," Greinke said. "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." 

...

"I definitely can't guarantee I'm going to get guys out no matter what the velocity is or whatever," Greinke said. "I'll do whatever I can and hopefully that works out." 

It should be noted this is not the first time Greinke's velocity has been down during spring training. It was down in the mid-to-upper-80s the past two springs as well. Greinke gradually built up arm strength and got his fastball back into the low-90s before long. Obviously the D-Backs are hoping for the same this year.

On one hand, few pitchers in baseball are as equipped to deal with reduced velocity as Greinke. He's never been a blow-you-away type of pitcher. Greinke is an artist who picks hitters apart with command and a deep arsenal. That should allow him to continue pitching effectively even with reduced velocity.

MLB: NLDS-Los Angeles Dodgers at Arizona Diamondbacks
Zack Greinke's fastballs has been sitting in the mid-80s this spring. USATSI

On the other hand, reduced velocity leaves any pitcher with less margin for error, no matter how well they command their heater or how many secondary pitches they feature. Pitching at an ace level -- which Greinke did last season -- with mid-80s heat is damn near impossible. Guys like Mark Buehrle are few and far between.

Opening Day is exactly three weeks away now, giving Greinke three more spring outings to get his fastball back up around 90 mph, where he usually sits. Chances are the velocity will come back eventually. But any time you're talking about a guy this age with that many innings on his arm, there's always some lingering concern until you actually see that velocity come back.