Allow me to recount the magical tale that was the 2015 season of Mike Pelfrey.
Pelfrey started that year on the outside of the Minnesota Twins' rotation looking in. He had been jettisoned to the bullpen, having lost a starting job to Tommy Milone. Pelf was none too pleased, but one 80-game suspension for Ervin Santana later, and it was back to starting for the tall righty.
Given Pelfrey's history (he hadn't posted an ERA on the sunny side of 4.00 since 2010), this got all of the daily fantasy baseball players giddy with excitement. They knew they could stack opposing offenses like crazy against this pup, and they weren't likely to be disappointed.
They were disappointed.
Pelfrey finished his first 11 starts of the season with a disgusting 2.28 ERA, leaving the eyes wet and the bankrolls dry of those who looked to pounce on his past struggles. Not that I'm speaking from experience or anything. Of course not.
What made this all the more frustrating is that every peripheral statistic backed up the perception that Pelfrey wasn't a top-of-the-line starter. He had a SIERA (which estimates ERA) of 4.49, a full two runs higher than his actual ERA, and he wasn't striking anybody out. How was this happening?
This caused me to start questioning whether I was looking at the wrong advanced stats when it came to evaluating Pelfrey. Sure, 11 starts isn't the biggest sample, but it's not small, either. Somehow, this guy was alluding the regression that every stat I trusted said was coming. Was he actually -- gasp -- good?
Patience would have been a nice thing to have here.
When the regression hit, it hit in a big way. Pelfrey posted a 5.62 ERA over his final 19 starts, even though his SIERA over that span was only slightly higher at 4.64. His performance didn't change much, but the outcome did.
While this is only one example, it's not an outlier in the slightest. Using advanced stats, we can better evaluate starting pitchers, whether it be for picking which to use or which to exploit with our offensive players.
Let's go through a few of these ever-so-crucial advanced stats so that we don't let the next Pelfrey to play with our minds again.