Mandatory Credit: Peter G. Aiken-USA TODAY Sports

There are many ways to discuss James Shields‘ importance to the Kansas City Royals. Personally, I like talking about how good he is at throwing a baseball. It’s not that I don’t like the veteran presence he brings, but I enjoy things that can be quantified, and there are only so many different ways to say “he’s a leader.”

Last year, Shields had a very good season. He had a 3.15 ERA in 228.1 innings, and without him, the Royals certainly wouldn’t have been within shouting distance of a playoff spot. However, there were some troubling signs that may have suggested a regression was possible. His strikeout rate fell to 20.7%, lower than it had been since 2009. His walk rate was higher than it had ever been. He allowed line drives at a higher rate than he had ever done before. And his strand rate was at 79.5%.

Not to mention the fact that Shields turned 32 years old over the winter, and had thrown a lot of innings in his career. I wasn’t necessarily expecting him to struggle this year, but it definitely wouldn’t have been the biggest surprise.

So far in 2014, that surprise has not arrived.

Shields has been outstanding this season, pitching 60.1 innings with a 2.54 ERA, 8.35 K/9, and 1.79 BB/9. His strikeout rate has bounced back to 22.8%, close to his 2011 rate, and his walk rate, at 4.9%, is lower than it’s been since 2008. He’s still allowing a few more line drives than you would prefer (21.8%), but he’s countered some of that by generating more ground balls (45.9%) and popups. In fact, his infield fly ball rate is much higher than it’s ever been before, currently sitting at 12.7%. And perhaps even more encouraging is that he’s having this level of success with a strand rate of 71.4%, meaning he isn’t just getting lucky with runners on base.

You know how a little kid will ask you a question, and after you answer, the next 43 questions to follow are “BUT WHY???” That’s my brain in situations like this. What is Shields doing that’s allowing him this level of success?

The first thing I noticed with Shields this season is that his fastball velocity is higher. It’s not significantly different (93.7 MPH this year, 93 MPH last year), but it’s not nothing. Also, velocity typically increases as the season progresses, so perhaps his average velocity will climb even higher.

In addition to a faster fastball, Shields has been using his cutter and sinker more frequently, while decreasing the usage of his other three pitches. In 2013, he threw a cutter 22.1% of the time, but he’s increased that to 29.5% in 2014. The increase is smaller with his sinker – up to 13.3% from 11.9% – but I do think there is some significance there, based on the results he’s getting with that particular pitch.

Last season, hitters were teeing off on Shields’ sinker, to the tune of a .435 batting average and a .588 slugging percentage. This season, however, he’s holding batters to a .243 AVG and a .378 SLG with his sinker. Shields is mostly throwing his sinker more frequently against lefties, but he’s throwing more cutters against both left- and right-handed batters. Oddly enough, when opposing batters put his cutter in play, they’re seeing better results than in 2013. The problem for them, though, is putting the ball in play.

Shields is getting whiffs with his sinker, curveball, and cutter more often than he did last season, all by roughly 2 percentage points. His whiff per swing rates are also much higher on those pitches this season. Shields’ overall swinging strike rate is down slightly from 2013, due in part to reduced whiff rates on his fastball and changeup, but because he’s showing the ability to miss bats with multiple pitches, his effectiveness has not eroded.

On the point of mixing pitches, Shields is starting batters off with more sinkers and cutters, and has basically abandoned his offspeed pitches on the first pitch. Shields is a very smart pitcher, so if hitters start to notice him throwing hard stuff in the zone on 0-0, he may start pitching backwards to keep them off balance. As it is now, he’s throwing first pitch strikes 63.4% of the time, which is the highest rate of his career. When a pitcher like Shields gets ahead early, batters are going to be in quite a bit of trouble.

Finally, we see that Shields’ fastball and cutter have been two of the more valuable pitches in baseball. His fastball currently is at 6.3 runs above average, which ranks 6th in the game, and his cutter has been worth 4.0 runs above average, which is good enough for 5th in MLB. Those two pitches have helped make up for his usually-excellent changeup, as it hasn’t gotten the kind of results we’re used to seeing.

Shields is off to a great start this season, and the reasons behind it are multi-faceted. He still may see some regression, particularly in the runs allowed department, but some of the concerning trends from last season have reversed. He’s mixing his pitches well, getting more desirable batted ball outcomes, and he’s even added a bit of velocity. When you also notice that he’s throwing more strikes, it’s easy to see how Shields is pitching like one of the best pitchers in the league.