​Last season was one of the Arizona Diamondbacks best in recent years. Sadly though, things aren't looking so great at this juncture despite the team having high expectations for 2018. 

J.D. Martinez is no longer in Arizona, but that's obvious. 

What Diamondbacks fans should be worried about now is All-Star ace Zack Greinke. 

I'm not typically the type of person to worry about athletes if they are underperforming, but when the athlete says they are nervous about an aspect that's paramount to their performance, that is really cause for concern. 

The right-hander's ​velocity was clocked in the mid-80's on Thursday morning for the second week in a row. That's not a good sign and nowhere close to where it needs to be. 

Greinke further spoke on the matter. 

"Every year, I get nervous that it's not working good enough and that it's not going to come fast enough. I definitely can't guarantee I'm going to get guys out no matter what the velocity is or whatever, I'll do whatever I can and hopefully that works out."

Not exactly the confidence that fans are looking for. 

With that said, don't go too crazy yet. Greinke has never had a dominant fastball, he has been more of an ​artist with his off-speed and location. 

However, with three starts remaining in the spring, he does need to build up that arm strength quickly.