By Nick Shepkowski–

(CBS) After looking like he was headed in the right direction in May, White Sox right-hander Jeff Samardzija has been a disaster in his first two starts in June. He’s allowed 15 earned runs and four homers in his 12 1/3 innings this month. For the season, he’s 4-4 with a 4.93 ERA and 1.36 WHIP.

So why has a 2014 All-Star turned into one of baseball’s biggest busts of 2015? One quick look at Samardzija’s FanGraphs page will answer just that.

In browsing the numbers, what jumps out is that Samardzija is throwing more cutters right now than he ever has previously. In fact, 25.7 percent of his pitches thrown this year have been cutters. That’s 11.3 percentage points more than any other time in his career. So must be that guys are hitting the hell out of that pitch, right?

Wrong. The cutter has actually been Samardzija’s second-best pitch this season, as he has a pitch value of +0.6 on the cutter. His best pitch has been his split finger fastball that ha a 1.2 value through Sunday. If you’re a bit new to what these numbers mean, pitch value is loosely a measure of the change in run expectancy from pitch to pitch. (For a more in-depth definition, click here.)

What’s alarming about Samardzija is two other pitches. Samardzija’s fastball has regressed back to what it was prior to 2014, and his slider is the least efficient it’s ever been.

We’ll start with the fastball. Despite often being perceived as a flamethrower, Samardzija’s two-seamer and four-seamer have been far from special. He has yielded a negative pitch value on seamed fastballs in all but two of his first seven big league seasons and now in his eighth one as well. It just so happens that 2014 was an anomaly for him with his fastball pitch value coming in at +9.3.  The only other year Samardzija’s fastball graded as a positive pitch was when he was a full-time reliever in 2011, at 1.6.

Other than that, it’s been regularly below average. Before 2014, his two-seam and four-seam fastballs combined to be a -26.0 pitch value, with his lowest score coming in 2012 when it graded out at -8.0. For some perspective, Samardzija’s on pace (if he makes the rest of his starts) for his seamed fastball to grade out at -13.1. That would be mark an astounding 22.4 drop in pitch value from 2014.

Kindly put, his fastball has been awful.

Perhaps the more alarming pitch is the decline of Samardzija’s slider. Entering 2015, Samardzija had combined for +24.7 pitch value with the slider, easily his best of any pitch.

At this point I think you know where we’re headed.

From 2011-’14, Samardzija’s combined pitch value on his slider was +25.2, an average of +6.3 per season, with it peaking at +7.9 last year. His lowest in those years was a still plenty respectable +5.2 in 2012.

And then there’s 2015.

Samardzija’s slider has gone from his most reliable pitch to one of his worst. Although it weighs in at -4.2 as a whole this year (slightly better than -4.6 with on the seamed fastball), his drop from where it has been the majority of his career is concerning. It’s a 12.1 drop from last year and a 10.5 drop from his average between 2011 and 2014.

I know there a lot of numbers involved in this piece, but hopefully it helps clear up where Samardzija’s problems stem from. If you still don’t understand then I’ll make a long story short for you:

The rise in cutters isn’t Samardzija’s problem, he’s simply throwing more because it’s been one of his best pitches. The most reliable pitch in his career (the slider) has been below average, and his seamed-fastball has regressed from being a great 2014 to being awful and much more in line with his career norm.

Nick Shepkowski is a weekend host at 670 The Score and produces The Spiegel and Goff Show each weekday from 9 a.m.-1 p.m.  You can find all of his work here and follow him on Twitter @Shep670.