Fangraphs website. At the top of that page there are tabs for Offensive stats, defensive stats, pitching stats, WAR, etc....
If you're just looking for a quick overview of the statistics presented in the article or in this thread so far I can give you my understanding of them (feel free to skip this post if you feel you already understand these statistics).
ERA is obviously the most basic and well known of the statistics available for pitchers. ERA+ and ERA- are essentially just ERA that has been changed into an easier to read/use format. So an average ERA is always going to be 100 no matter what year you're looking at. ERA+ comes from baseball-reference.com and better pitchers are given values >100. ERA- comes from fangraphs.com and for this statistic better pitchers are given values <100. Otherwise they are very similar statistics with some small nuances.
However ERA is very dependent on factors outside of a pitchers control. The ballpark he pitches in, his defense behind him or just random luck, does a ball fall in for a hit when it shouldn't? Which is called babip or batting average on balls in play. Essentially when contact is made what percentage of the time does it fall for a hit.
To eliminate those factors people started to creat DIPS theory, or defense independent pitching statistics. The most popular of these currently are FIP and xFIP. The theory at the time these statistics were created was that pitchers could only control how many batters they struck out, walked and how many home runs they allowed.
Accordingly the FIP formula only takes those 3 things into account to determine how well a pitcher actually pitched. Then there is some fancy math done to make the result look like a traditional ERA number. So if a players FIP (let's say a 5.18) is bad on an ERA scale (an ERA of 5.18 is obviously awful) then it is also a bad FIP number.
xFIP is the same thing as FIP except that it includes how many home runs a pitchers should have given up based on league average home run rates instead of how many home runs a pitcher actually gave up. This makes strikeouts, walks and flyball rate the only factors that matter. For a several years this was the go to stat. It was the best at determining how well a pitcher actually pitched as well as the best at predicting the next seasons ERA.
Some types of pitchers didn't seem to play nicely with FIP and xFIP, however. Knuckleballers and players like Tim Hudson consistently seemed to have lower ERA's than their FIP or xFIP suggest they should have. It has since been acknowledged that pitchers can control how many groundballs they produce versus how many flyballs and line drives. Fly balls are turned into outs the most frequently but they can also go for home runs and extra base hits. Line drives are clearly bad all around. Ground balls, while going for hits slightly more frequently than fly balls, rarely turn into extra base hits and never into home runs. So after quite a bit of research and debate it was determined that ground ball pitchers allow fewer runs than fly ball pitchers, all else being equal, and that it is a controllable skill.
That bred the most recent statistics like tERA (the "t" stands for true) and the latest, and currently best (at least that I am aware of), statistic called SIERA. These use a pitcher's strike out, walk and home run rates, just like FIP and xFIP, but it also adds in how a pitcher pitches. Is he a ground ball pitcher or fly ball? What's his line drive percentage? It also takes into account what stadium a player pitches in. A home run at Yankee Stadium might not be a home run at Target Field.
FIP, xFIP, tERA and SIERA are all known as ERA estimators as they are attempting to determine what a pitchers true skill level was. As such these can be used, cautiously, to determine what a pitchers following season will look like as well.
There is another line of thought however. Some people don't care about ERA because it is too vague of a statistic. A home run is a home run; the previous statistics don't differentiate between a home run allowed when your team is winning 7-0 or when your team is tied in the bottom of the 9th inning. Clearly the home run when you're up 7-0 means much less than a home run in the bottom of the ninth of a tie ball game.
There are two basic premises of Win Probability Added (WPA) and similar stats. First, a pitcher (or batter or fielder as these stats work equally well for offensive players) is more valuable, in either a positive or negative way, in close or late game situations than he is early on during the game or in blow outs. This is referred to as the Leverage Index. The later in the game and the closer the score the higher the Leverage Index.
Second, because we have an extensive history of the play by play of baseball we can determine the average outcome for any given situation. We can then compare how much better or worse Mike Pelfrey did than the average pitcher. Another way to say that is we can determine how much Mike Pelfreys actions affect the Twins probability of winning a game, for better or worse, when compared to an average pitcher. Imagine Pelfrey faces a bases loaded situation. We can look back and determine what an average pitcher actually did in that situation, let's say the generic pitcher gave up a hit and 2 runs. If Pelfrey strikes a batter out we know that he actually increased the Twins odds of winning the ball game when compared to the generic pitcher that allowed 2 runs. If Pelfrey's next pitch is hit for a home run he has now decreased the probability of the Twins winning compared to the generic pitcher. When you add up all of the changes in probability throughout a game, or season, and then factor in the Leverage Index you get the stat Win Probability Added. For WPA a 0 is average and for every whole number above zero one win has been added to the team's win total. Similarly every number below zero is a game lost that an average pitcher wouldn't have.
Well I didn't mean to write a novel, but for the second time today it seems I have. I didn't touch on all the statistics but those are several. If you have questions about any others or feel I misrepresented a statistic above feel free to ask or correct me. Again, sorry for the novel.
I feel something has to be wrong if on Fangraphs Pelfrey is a 2.1 WAR and on Baseball Reference he was a -0.3 WAR.
We can argue all we want about Pelfrey, and I bet he'll throw better next year, but the key is we have to get better pitching. If we re-sign Pelfrey we are doing nothing but accepting a mediocre pitcher who will give us little chance to be elite. We have to get someone better or we have the same pitching rotation as last year (plus one unimpressive FA pitcher). And that was a 90 loss rotation.
I could probably tolerate a Correia type contract since he's roughly that level of pitcher and the Twins are short on actual MLB capable pitchers. But regardless of his quick return from TJ and the hope that he will do better next season he literally has no upside as a starter. He's 30 (in January) and literally has no upside beyond innings eating #4/5. A significant multi-year contract would work out as well as the Blackburn contract.
tbh I want nothing to do with a guaranteed 2nd yr (like Corriea) but I'm already resigned to the Twins bringing him back and that's what it will take. If the guaranteed money is >15M then this board will be unreadable for a week and i will likely contribute to that nonsense.
I go either way on Pelfrey and his 2.1 WAR.
Perkins had 36 saves in 40 save opportunities in 2013
Perkins also had a 1.7 WAR (wins above replacement).
therefore, any other bullpen guy or chump off the street coulda come in and saved 34 out of 40 games last year, am I understanding that correctly?
It's too early in the offseason to want to bring back Pelfrey. At this stage, my hopes are way higher. I don't mind Pelfrey. I have a hard time watching when he pitches, but if he can be as good in 2014 as Correia was in 2013, that would be solid. Like Nick said, if he's your 4th or 5th starter, that's fine. But I certainly wouldn't go multi-year, or much (if any) more than he got last year. Just not enough upside. But, one thing it is clear that Terry Ryan likes is a pitcher who can throw 180+ innings. And that's understandable. Meyer, May and Gibson should be up in 2014. It'd sure be nice for them to not be the top three pitchers in the rotation.
Pelfrey for multiple years is completely ridiculous. And Pelfrey for one year . . . is actually more ridiculous. If the Twins sign FAs to one year deals, then the same damn thing is going to be asked next year going into 2015. This is the time to invest in 3 or 4 years of pitching. This is THE DAMN TIME TO DO SO. Even the owner is willing to do that!
Pelfrey is worth 0.0 WAR next year. And that might be nice. The Twins can easily get that from a guy making 500k.
So save that 5 or so million bucks, take the 5.5 million bucks from the end of Nick Blackburn, splurge another 5 million or so and you get Ervin Santana or Ubaldo Jimenez per year. Or you get Hughes and Feldman or something. Why is this such a difficult concept to grasp?
The Twins, hopefully, will learn from the Gibson nonsense of 2013 and not do the same to Meyer. Gibson should have been given 100 innings of MLB time in 2013, but they failed to figure out a way to do so. Same for Meyer this year.
May can be up midseason and would be an instant improvement over everyone in 2013 other than Correia and Deduno.
If I were in charge--and had balls--I would declare Kyle Gibson the opening day starter and let it fly.
Thanks Oxtung. Good stuff.
I had actually stayed with Berardino until he hit SIERA, then it got too much for me.
There's a reason I took stats for social science majors rather than the harder version.
Of the other 29 teams how many of them have fans talking about how good it would be to bring in Pelfry as a free agent this winter? My guess zero.
Time to move on for him!
I'm not sure why there can be some much variation on some pitchers. Radke has 45 WAR on both, for example. Santana is only a 3WAR difference.
I've read (but not sure it's true) suggestions that fWAR gives too much credit to bad pitchers although both rated Blackburns 08-09 seasons basically the same. fWAR isn't as harsh on Blackburn's disastrous 2012. And I've also read that stat heads like fWAR more than bWAR. So who knows.
Now my basic statistics was quite a few years ago, so please feel free to correct me. In any of these ERA predictors you have to consider their correlations SIERA is said to be 0.72. Good, but hardly precise. There is a regression factor. RMS data shows that factor to be greater than 1 for all the calculators for IP less than 200. Standard deviation of 0.5. Essentially their measurement could be up to a 0.5 worth of ERA wrong. One way or the other. 4.64 by SIERA is the predictive value, by deviation then the predictor says anywhere in the 4 range. Now SIERA does not ignore balls in play. To be an accurate predictor things have to be static. The one thing Twins fan hope for is for is for things not to be static. The predictors say he will be a better pitcher than last year. None say he will be a great pitcher. That is about all you can take away from this.
WPA doesn't explicitly use the Leverage Index. It instead is automatically built into the way WPA is calculated. For instance, if the Twins hit a home run in the first inning their chances of winning go up but not dramatically because there are still 8 innings to play. So the WPA added for that home run is small. On the other hand if the Twins hit a home run in the 9th inning of a tied game their probability of winning that game increases significantly. So the WPA add for the 9th inning home run would be significant.
So you can see that Leverage Index, which is in itself a statistic, is not actually used in the Win Probability Added statistic. I was simply trying to show that late game and close game situations are more valuable than early or blow out situations.
There is a statistic, WPA/LI, that uses both Win Probability Added and Leverage Index. It attempts to strip the late and close game bonus that is automatically a part of WPA out so that 2 players contributions can be compared even if they don't fill the same roll on a team. For instance, Ryan Pressly pitched almost exclusively in low leverage situations. That isn't his fault, the manager made those decisions. So what if you want to compare him to Glen Perkins? Well if you use WPA Perkins (2.8 WPA) is clearly going to be better than Pressly (0.2 WPA) because Perkins was frequently in high leverage situations. So WPA/LI is a way to remove the advantage that Perkins gets and puts them on a level playing field. So what does WPA/LI say about Pressly (0.5 WPA/LI) versus Perkins (1.2 WPA/LI)? Well as you can see Perkins was still a better pitcher than Pressly even if they were used in the same roles.