Mike Fiers or Marco Estrada for the Future?

The Brewers current rotation might be the most fascinating group in baseball at the moment. With Chris Narveson and Shaun Marcum on the DL and Zack Greinke in Anaheim, the team has had to turn to three unproven big league starters to fill out their rotation – Mike Fiers, Marco Estrada, and Mark Rogers. Generally, when you move a guy from the bullpen to the rotation and call up two kids from the minors, the results aren’t great, but Fiers, Estrada, and Rogers have been fantastic, and the team hasn’t seen a real drop-off by going with the kids.

Fiers has gotten the most attention, as he’s run off nine straight starts with at least six innings pitched while allowing two runs or fewer, posting a 1.03 ERA over that 61 inning stretch. And, certainly, Fiers story deserves to be told, especially considering his 88 mph fastball and general lack of pedigree as any kind of top prospect. His eye-popping 5/1 K/BB ratio without big time stuff has made him a central topic of discussion, and rightfully so. However, when I was looking at the list of guys who have posted similar statistical seasons to Fiers, I couldn’t help but notice that Estrada was on that list too.

To filter out Fiers-like pitchers, I looked at starting pitchers over the last 11 years who have posted a walk rate below 6%, a strikeout rate above 20%, and a ground ball rate below 35%. Essentially, this skill set is strike-throwing fly ball guy who misses more bats than you might expect due to location and deception, and the other names who have had similar types of seasons are all pretty good pitchers — Ted Lilly, Scott Baker, Colby Lewis, and Phil Hughes. But, those four are joined not just by Fiers, but also by Estrada, who is having a very similar season to Fiers in some ways.

If we look at them side by side as just starting pitchers this year, the comparison looks like this:

In four of the five main variables that drive run prevention, Fiers and Estrada are nearly equal. However, Fiers has a 1.82 ERA as a starter, while Estrada checks in at 4.40. The difference? The long ball.

Fiers’ HR/FB rate is just 3.6%, while Estrada checks in at 15.8%, which translates to an extra 12 home runs allowed for Estrada despite facing 22 fewer batters. The average home run generates about 1.4 runs of offense, so we’d have expected those 12 home runs to lead to an extra 17 runs allowed for Estrada, while the actual gap is 20 runs allowed. In other words, nearly all of the difference in run prevention between the two is home run prevention.

We can be pretty sure that neither of these guys are going to keep giving up home runs at their current paces. Even if Fiers was the second coming of Matt Cain (career 6.8% HR/FB) or Jered Weaver (7.5%), we’d still expect him to be north of 8% simply because of the ballpark he’s playing in. And, of course, 70 innings isn’t near enough of a sample to conclude that Fiers’ home run prevention skills make him another exception to the rule.

With Estrada, we have a little more data that points to a home run problem not being a complete fluke, as 12.5% of his fly balls had gone for home runs even before this season began, so this isn’t entirely new for him. Of course, we’re still dealing with a career total of just over 200 innings, so we don’t want to say that Estrada is definitely the new Brett Myers just yet. Most likely, Estrada’s home run rate is going to come down while Fiers is going to go up, but you know all of this already.

But, the question remains: if the Brewers have to just pick one for their 2013 rotation — this is a hypothetical, as they can of course have both if they want — which one would you rather go with? The 2012 performance results obviously point to Fiers, but the stuff points to Estrada, as his fastball is two full ticks higher, and he’s generated more swings and more swinging strikes than Fiers as a starter. Estrada also has a longer Major League track record of missing bats, while Fiers is running a higher strikeout rate in the Majors than he did in Triple-A, which is fairly unusual.

You can make arguments for preferring the long term future for either one. I’m honestly not sure what side I’d come down on, so let’s put this to a poll. Pick one – Michael Fiers or Marco Estrada. Who you got?