Will the Twins’ de facto ace retain his label as the club’s top starter or descend into mediocrity this year? Let us take a deeper look.

2012 Recap
Diamond gained little consideration for a big-league job in spring training after going 5-19 with a 5.44 ERA between Triple-A and the majors in his first year with the organization. So, he reported to Rochester and started his season on a tear, going 4-1 with a 2.60 ERA while flashing much improved control in his first six starts.

That was plenty to earn him an invitation up north, where a bloodied staff was looking anywhere it could for bandages. The lefty was that and more, rattling off a 5-1 record and 1.61 ERA in his first seven starts. He continued to pitch well deep into August before a bit of a rocky finish.

Diamond was bound to cool off, but the let-up didn't come in the form of a ghastly regression to the mean, as he still finished with very strong numbers. At the end of the year, Twins brass made it clear that Diamond was the only starter who had guaranteed himself a spot on the 2013 staff.

In a season where just about everything that could possibly go wrong in the rotation did so, Diamond was a breath of fresh air. Contrasting sharply with most of his injured or fledgling counterparts, he rebounded from a brutal year to become a shockingly steady force.

To say he was the rotation's rock would be an understatement; he threw 64 more innings than any other Twin despite spending his first month in Triple-A. It's a success story that the club will cling to as they hope to get lucky with several wild cards this year.

Why He’ll Be Worse
This is a pretty straightforward case for anyone with an understanding of statistical probabilities in baseball. Diamond held one of the lowest strikeout rates among all MLB starters, but was able to limit the damage on balls in play by inducing lots of grounders and handing out very few walks. His GB rate (53.4 percent) was among the top ten in the majors and his walk rate (1.6 BB/9) was the lowest in the American League.

Diamond has posted strong grounder rates throughout his career but it's tough to be elite in that category from year to year, especially as hitters make their adjustments. His phenomenal walk rate was out of character with previous norms; in fact, his mediocre control in the Braves organization is probably a big reason they were willing to part with him.

To turn around and become one of the most prolific strike-throwers in the majors is either a remarkable triumph of dedication and coaching, a fluke, or both. Any regression in walk rate or BABIP will decrease his margin for error, at which point an inopportune extra-base hit here and there can dramatically change his results.

It's the nature of a pitch-to-contact hurler relying on control and grounders. As a relevant example, think of how volatile Carlos Silva was from year to year.

Why He’ll Be Better
Let’s be honest: there’s almost no chance Diamond will be better than he was last year. While everything was going wrong for everyone else in the rotation, everything was going right for him and the odds that he’ll be able to match his core statistical marks from 2012 are extremely low.

What fans and coaches are hoping is that Diamond can maintain, or regress modestly, and remain a quality mid-rotation starter while logging 200 innings. As long as his BABIP doesn’t skyrocket and he can keep the BB/9 mark down, that’s a perfectly realistic goal. The ground balls are more than likely going to be there, as he has demonstrated throughout his career a keen ability to keep the ball down, which also prevents many from leaving the park.

There's a conception that stat-driven analysis is overly focused on strikeouts, and fails to give much consideration to any other aspect of pitching performance. But Diamond's 2012 season was the perfect example of the things a stat-head would look for in a guy that doesn't rack up a lot of whiffs.

He pelted the lower regions of the strike zone, resulting in weaker contact and few free passes. This approach also yielded extremely low pitch counts (he never totaled more than 104 in a start despite completing seven-plus innings 13 times), and you know how much the Twins appreciate that.

Diamond's successful 2012 season was characterized by his ability to throw strikes, get ahead in counts and challenge hitters. Will the new season establish his strides in those departments as trend or mirage? That's the question that could very well dictate whether he's an asset or a liability.