FIP and ERA, and a drop in his WAR. So, let’s ask the question: just what exactly is going on with Justin Verlander?

First, let’s note that Verlander isn’t having a bad season. He just isn’t looking like the dominant Justin Verlander of old. Let’s compare some important rate statistics he had from 2009 to 2013 against those he has now in 2014:

Verlander’s walk and home run rates have increased slightly, but not tremendously. He’s still getting ground balls at his usual rate, and nothing’s really changed about his HR/FB rate. What’s truly effecting his FIP and, therefore, his WAR, is his strikeout rate. Verlander is now striking out approximately two fewer batters per nine innings than usual. What could be the cause of this?

Let’s take a look at the effectiveness of Verlander’s pitches more closely by examining his pitch type linear weights from 2013 and 2014:

While the effectiveness of all of his pitches has declined, Verlander’s curveball has seen the biggest decrease in runs saved per 100 pitches. Similarly, his fastball is now below average for runs saved. Does this mean the fastball and the curveball are the root of his strikeout problems? Below are the individual swing and miss rates for each of Verlander’s pitches:

We see that people are swinging and missing at Verlander’s curveballs at about the same rate as last year, but not so much at his other pitches, especially his slider. Then why has the quality of Verlander’s curveball declined so much? Well, it’s mostly a matter of strikes and balls. In 2013, Verlander threw his curve for a strike 64.61% of the time, while in 2014, that number fell to 56.56%. So while Verlander’s curve still has enough movement to miss bats, batters just don’t have enough incentive to swing at it as often (batters are swinging at the curve almost 3% less than they did in 2013).

As for Verlander’s fastball, it's possible that a decrease in velocity is responsible for its decline. In 2013, his average fastball was 94 MPH while in 2014 it’s 93.2 MPH. Is a decrease in 0.8 MPH really enough to degrade Verlander’s fastball to the extent we’ve noticed, especially in terms of strike outs? If Verlander continues to throw his fastball at the same rate or higher on two-strike counts, then this may be the case. In 2013, he threw his fastballs in two-strike counts to lefties and righties at respective 51% and 37% rates. In 2014, those rates are 47% and 40%. So even though he's throwing it slightly less often to lefties, he's actually throwing it more often to righties This may be one of Verlander’s biggest problems.

Despite decreases in his velocity across all of his pitches but his changeup, Verlander hasn't truly changed how he pitches in each count (especially two-strike counts). Since his slider is now his only above average pitch, he needs to rely on it more often in two-strike counts, rather than his fastball. So far in 2014, Verlander is using his slider 8% of the time in two-strike counts against lefties and 33% of the time against righties.

If Verlander wants to be more successful and adapt to a declining velocity that will only further worsen in subsequent years, he needs to throw his slider and curveball more frequently for strikeouts and accept that his fastball is turning into a contact pitch.