Should I rely on Earned Run average or opponent average for a pitcher?

[dumbrabbit]

What the title says. Which stat would be a good starting point for finding a good pitcher, ERA or opponent average?

[ryanivr]

Originally Posted by dumbrabbit

What the title says. Which stat would be a good starting point for finding a good pitcher, ERA or opponent average?

Neither. Use FIP.

[ryanivr]

To explain: Both ERA and opponent's AVG are heavily influenced by the defense behind them. They are largely influenced by luck.

There's a LOT of noise when a hitter hits the ball in play. To evaluate a pitcher, you want to eliminate as much of that noise as possible. That's what FIP does. It removes the defense from the equation and relies on the things a pitcher can control; Strikeouts, Home Runs Allowed, and Walks.

FIP assumes that balls hit in play were league average, and tells you what the pitcher's ERA should have been if that were true.

You can use this along with ERA to determine a few things. If a pitchers ERA is 2.50 and his FIP is 4.00, you're looking at a pitcher that got very lucky OR had a tremendous defense behind him. If you have a guy whose ERA is 5.20 but his FIP is 3.75, you're looking at a pitcher who probably gives up a lot of singles and has a pretty lousy defense behind him. You can then use that to determine a general expectation for the future.

[dumbrabbit]

Never mind

[dumbrabbit]

Okay let me get this straight: ERA determines pitcher's earned run average, while FIP helps determine whether he has a good/bad defense, right?

[Tyler87898]

Originally Posted by dumbrabbit

Okay let me get this straight: ERA determines pitcher's earned run average, while FIP helps determine whether he has a good/bad defense, right?

FIP is basically saying how good a pitcher is actually pitching on a scale comparable to ERA. If a pitcher has a high ERA and a low FIP, it usually means they're unlucky/have a bad defense behind him. If its vice versa, it usually means the pitcher is lucky/has a good defense behind him.

xFIP (which is not in the game) I believe is a good predictor of future ERA (I think...).

EDIT: I'm pretty sure this is exactly what ryanivr said so I don't know why I posted this, but whatever...

[dumbrabbit]

I gotcha now. So FIP usually outweighs era on the luck scale.

[dumbrabbit]

What about a low era/low fip and vice versa?

[damientheomen3]

Originally Posted by dumbrabbit

What about a low era/low fip and vice versa?

Low ERA and FIP pretty much confirms that it was the pitcher's performance that resulted in their great season (so if you're negotiating with them, it pretty much shows they're worth it) while high ERA and FIP obviously would show that it's the pitcher that stinks, and not that they're getting screwed by luck or defense.

[ryanivr]

Originally Posted by dumbrabbit

What about a low era/low fip and vice versa?

If FIP is low with a low ERA as well, that means the pitcher is freakin' good.

Long version: It means that the pitcher's skill is influencing ERA more than anything else (Which is good!). It means there's not a lot of noise influencing his ERA.

Think about it like this: ERA is a very simple method to evaluate a pitcher. Does it correlate to pitcher skill? Absolutely. But what correlates even BETTER to a pitcher's skill? FIP.

So here's three scenarios:

FIP close to ERA: A pitcher whose ERA is relatively indicative of his actual skills.

FIP < ERA: A pitcher who got unlucky on balls hit in play AND/OR has a crappy defense behind him.

FIP > ERA: A pitcher who got very lucky on balls hit in play AND/OR has a good defense behind him.

So, let's say you've got $20mil to sign a pitcher and there's three guys on the market that you like. At first glance you might look at their ERA, but you'd be well served also looking at their FIP. In fact, you can probably JUST look at their FIP.

Now, let's say you have a pretty good rotation signed, and they've got good rating, but for some reason, they're all putting up 4.50 ERAs. Not horrible, but certainly not good either. They're ratings tell you that they should be really good. That's when you can check their FIP and actually use it in conjunction with ERA to figure some things out. If their FIP's are all lower than their ERA's, it's highly likely you have a problem on defense. And it's not errors that you're really worried about, it's range.

[hopeful1212]

Originally Posted by dumbrabbit

Okay let me get this straight: ERA determines pitcher's earned run average, while FIP helps determine whether he has a good/bad defense, right?

ERA is a measure of what actually happened. It's how many runs the pitcher as given up (without errors being the deciding factor in the scoring) per 9 IP.

FIP is also a measure of what actually happened. However, it only looks at the pitcher's BB, K, and HR allowed. Other factors such as fielding, BABIP, or the sequencing of events (such as whether all the hits came in bunches or were spread out) aren't included.

Basically if you want to know who's given up fewer runs in the past then ERA will tell you that. If you want to know who is most likely to give up fewer runs in the future then look to FIP.

[hopeful1212]

Originally Posted by dumbrabbit

What about a low era/low fip and vice versa?

If a pitcher's FIP and ERA are similar this generally means that they have had average luck and fielding. Generally, over a pitcher's career you should see career FIP and career ERA converge as the luck and the fielding strength behind them "average out".

If the FIP/ERA are far apart then you're either looking at good/bad luck and or good/bad team fielding.

Of course, if the sample size is really small, then even FIP won't tell you much.

[olivertheorem]

I usually look at FIP first, then BABIP and GB% (by which I mean G/F in the available stats, not the GB% on the profile page).

[bazeall]

"So, let's say you've got $20mil to sign a pitcher and there's three guys on the market that you like. At first glance you might look at their ERA, but you'd be well served also looking at their FIP. In fact, you can probably JUST look at their FIP."

Why not look at their ratings?

[olivertheorem]

Because depending on scouting settings, the ratings can lie.