Being an Oakland Athletics fan means that you can't get too attached to your players. Until and unless the team gets its new ballpark (or an owner who cares at least a little bit about baseball), we fans will be forced to watch the cycle repeat itself, over and over:
- Develop minor league prospect into Major League star
- Enjoy Major League star for 3-6 years
- Watch Major League star approach expensive free agency and become the subject of trade rumors
- Trade Major League star for new minor league prospect(s)
- Develop minor league prospect into Major League star
When comparing two players (especially a rookie against a veteran), there are two ways to look at it. You can see who is currently having the better season, or you can try to determine which pitcher is actually better, based on underlying performance (like fielding-independent pitching or deviation from career norms) and future expectations. Bartolo Colon is undeniably having a better season than Tim Lincecum, but I wouldn't say that Colon is a better pitcher. He's not a better pitcher now, and he won't be a better pitcher in the future, for a variety of reasons.
It is easy to look at these two pitcher's ERA's and wonder why it is taking me more than one sentence to settle this debate. Here's what I mean:
Parker: 2.57 ERA, 156 ERA+
Cahill: 3.67 ERA, 115 ERA+
Gosh, it's not even close. Parker's ERA is a full run lower, and his ERA+ (which is adjusted for ballpark and league) suggests that the difference isn't just a factor of pitching in the Coliseum. In terms of run prevention, Parker's results have been way better than Cahill's so far in 2012. That is a fact.
Ah, but there is more to it than that, isn't there? ERA only measures the results of what happened on the field (including the contributions of the rest of the team), not necessarily how well the pitcher actually pitched. I could walk the bases loaded with two out and give up a fly ball to the wall, but if my awesome outfielder makes a leaping catch to rob a grand slam, my ERA will be the same as the guy who struck out the side on 9 pitches. That other guy clearly pitched better than I did, though. That is about the most extreme example possible, to prove a point about the shortcomings of ERA as an analytic tool.
While these two pitchers have a huge ERA disparity, their fielding-independent stats (strikeouts, walks, and homers) are actually quite similar:
Parker: 7.1 K/9, 4.4 BB/9, 1.61 K:BB. 0.4 HR/9
Cahill: 6.6 K/9, 3.6 BB/9, 1.84 K:BB, 0.6 HR/9
Parker has the edge in K's, Cahill has walked fewer hitters, and neither has shown much interest in allowing home runs. Considering that their ERA's are separated by more than a run, these two pitchers have been surprisingly similar. Another way to illustrate how close their performances have been is a stat called FIP (Fielding Independent Pitching), which measures what a pitcher's ERA "should" look like if you remove the things he can't control (balls in play) and only focus on strikeouts, walks, and homers:
Parker: 3.56 FIP
Cahill: 3.73 FIP
Parker still has the edge, but the gap no longer looks so wide. Still, though, it seems that we can settle the first part of this debate: Jarrod Parker is definitely having a better season than Trevor Cahill, up to this point. Is that likely to continue? Let's start by explaining why the difference in FIP is so much smaller than the difference in ERA:
Parker, 2012: 6.5 H/9
Parker, minor-league career (366 innings): 8.4 H/9
Cahill, 2012: 7.9 H/9
Cahill, career: 8.5 H/9
One reason why Parker has had so much success is that his batted balls aren't resulting in hits. There are pitchers in the world who can consistently limit hits (Matt Cain and Clayton Kershaw are two notable examples), but Parker has never been one of them. Parker has always lived within the "average" range of allowing hits in the minors, and it's unlikely that he has suddenly discovered the ancient Koufaxian secret to hit prevention as a rookie in the Majors. What is more likely is that more hits will start to fall in, and that the 6.5 number he's sporting right now will rise above 7 and start chugging toward 8. Cahill, on the other hand, is well within the normal range for his career. His rate of allowing hits is totally sustainable, and in fact wouldn't even be his career best (he allowed only 7.1 H/9 in his dominant 2010 season).
All of that is accounted for in the FIP stat, though. Even with Parker's fluky hit prevention, he's still pitching better than Cahill is. There is some more bad news, though:
Parker, 2012: 94.1 innings pitched (combined, Oakland and Sacramento)
Parker, career high: 130.2 innings pitched (in 2011)
With rookies, there's always a "but" at the end. Everyone has a "butt" at the end, but rookies have an extra "but" in addition to that. They have usually never played a baseball season which is as long as the 162-game Major League season. After missing all of 2010 while recovering from Tommy John surgery, Parker is even further behind. He has never exceeded 130 innings in his life, which means that after 5 or 6 more starts, his arm will be in uncharted territory. Uncharted territory is a bad place for a young pitcher's arm to be, as it usually results in declining performance. Every year, a handful of rookies put up amazing numbers in the first half of the season, and then tail off in the second half. This is a completely normal part of the development process, so much so that teams usually limit the innings of their young pitchers in order to avoid these declines (but mostly to protect the health of their arms). The Washington Nationals publicly announced this spring that Stephen Strasburg would be limited to 160 innings, regardless of whether the team is in a pennant race in September. Like Parker, Strasburg is a young pitcher coming off a recent Tommy John procedure. It would probably take Parker 10-12 more starts to reach that same 160 inning threshhold, which would take him through approximately the end of August. If I had to guess (and I am literally guessing, because I haven't heard any specific announcements from the team on this topic), Parker will play through August and be shut down for September, no matter how well he is pitching. And at that point, he will probably not be pitching as well as he is pitching now, because his arm will be getting more and more tired.
That brings us to decision time. Cahill is having what I believe to be his completely "normal" season. This is exactly average for him. If everything goes right, he can pitch like he did in 2010. If everything goes wrong, he'll pitch like it's 2011. This year, he has found his true ability, in my opinion. That true ability is solid, above average, but not an ace (more like a #2 or #3 starter). Parker is taking the league by storm, but there are warning signs which suggest regression. There is also time for him to improve his control, lower his walk rate, and take the next step toward being a true #2 starter (or even, possibly, a #1, depending on how much he cuts those walks). My final ruling: Parker and Cahill are roughly equal pitchers right now, which is a huge win for the A's. Parker is having the better season so far, but Cahill will finish 2012 with better numbers. In 2013, Parker will have a better season than Cahill, and will be the better pitcher moving forward because he will improve his control.
It would appear that Billy Beane pulled off the ultimate veteran-for-prospect swap, by receiving a rookie who is already matching the performance of the veteran he replaced just months after the trade went down. I think I need to go sit down; this Ferris wheel is going way too fast for me.
*The Parker-Cahill Conditional Relationship, expressed as an if-then statement: