One of the biggest trends in fantasy baseball over the past several years has been the development and use of deep analytic statistics. If you’re going to be a successful fantasy baseball player, you’ll need to use sabermetrics as part of you player evaluation process. and MLB’s are two great resources that will help you go behind the scenes and look beyond the traditional old school stats.

We’re going to focus on some of the deeper stats that you can use in your fantasy baseball pitcher assessments. Fangraphs features ERA estimators FIP, xFIP and SIERA on their pitcher player pages. These stats attempt to truly measure a pitcher’s performance by determining what a pitcher’s ERA would look like if he pitched in a setting where he experienced league average results on balls in play. They take a pitcher’s performance and presume he’s supported by league average defense and not effected by good or bad luck. ERA estimators attempt to answer the question “could you imagine how good “pitcher X” (who pitches for a last place team) would be if he pitched for “the best team in the league”.

These estimators, are valued on the same scale as traditional ERA. The lower the number the better.

Each of these estimators is calculated by using slightly different formulas and their results reflect that. In the case of xFIP, the assumption is that a pitcher is working in an environment with average home run per fly ball ratios. SIERA is park-adjusted, and takes into account that there will be times when pitchers pitch in traditional hitters parks (Coors Field), and other times when they pitch in pitchers parks (Petco Park).

With three and a half months left to the fantasy baseball season we should have a realistic view of what’s lacking on our fantasy baseball team rosters. There’s only so much available on the waiver wire every week, so at this time of the season we need to start thinking about improving our fantasy teams via the trade route. These estimators could be one of the tools we can use in order to determine the player that we might want to sell high or buy low. They aren’t perfect, but they can provide additional insight which can help sway our trade decisions one way or the other.

Let’s look at these ERA estimators in action as we identify some pitchers who’ve gotten off to a rough start so far this season and who might be poised to turn things around.

We’ll use Red Sox starter Eduardo Rodríguez as our primary example and identify several other pitchers who also might have some upside for the rest of the season.

Rodriguez has won six of his 10 decisions but he owns a 5.00 ERA and 1.39 WHIP. His FIP (3.77), xFIP (3.68), and SIERA (3.95) all indicate that he’s pitching much better than his ERA suggests. Some of his other stats also suggest that there may be better days ahead for Rodriguez.

For instance, his batting average on balls in play (BABIP) is .048 points higher than his career average. That hints that a bit of bad luck may have caused his ERA to balloon. His chase rate or O-swing % (percentage of pitches opposing batters swing at) and swinging strike rate or SwStr% (percentage of strikes that were swung at and missed) are all at career highs.

On the negative side, even though his velocity is virtually unchanged since last season, opposing batters are getting around on his fastball. Last season the BAA his fastball was .232. This season its .319. In fact, opposing batters are having better success against all of his pitches this season as compared to last, except for his sinker.

Cumulatively, Rodriguez’s ERA estimators put his overall ERA at just under four, and based on the mixed bag of stats that we just analyzed they might be correct. He may not be as bad as his 5.00 ERA suggests, but he’s no ace either.

Mets starters Zack Wheeler and Noah Syndegaard have both had disappointing seasons thus far. Wheeler was highly sought after in preseason fantasy drafts but is pitching to a 4.87 ERA. FIP, xFIP and SIERA all suggest that his ERA should probably be in the high three range. Syndegaard has a 4.45 overall ERA but the three ERA estimators are all below four. Buy low on these two underachievers perhaps? Tread lightly.

Brewers starting pitcher Brandon Woodruff is enjoying a breakout season with an 8-1 won-loss record and a 3.87 ERA. His K/9 rate is over 10, he’s cut his walk rate this season and he doesn’t give up the long ball. All three ERA estimators suggest that he’s pitching better than his current ERA which per their estimates, should be in the mid three range. If you own Woodruff, hold him. Otherwise he’s a good trade target.

Many were anticipating a big breakout season from Indians starter Shane Bieber this season. He’s striking out a ton of batters (11.2 K/9), exhibiting good control (2.3 BB/9) but he’s been victimized by the long ball (1.9 HR/9). He owns an ERA of 4.07. His xFIP, which per Fangraphs “replaces a pitcher’s home run total with an estimate of how many home runs they should have allowed given the number of fly balls they surrendered while assuming a league average home run to fly ball percentage”, is 3.44. His SIERA is 3.42, but his FIP is 4.21. When determining whether to buy or sell is Bieber a case where as Meat Loaf suggested “two out of three ain’t bad”? The Indians offense leaves a lot to be desired but that high strikeout rate is enticing.

Twins starter Kyle Gibson has won six of his nine decisions but has a 4.14 ERA and a 21.6 HR/FB rate (14.8 is the league average). Not surprisingly his xFIP is much lower than his ERA (3.43). His FIP suggests his current ERA is representative of his season long performance, but his SIERA indicates he’s pitched better than that (3.77). Based on the run support he’ll get from the potent Twins offense, Gibson might just be a better trade target than Bieber this season.

ERA estimators can also be used to predict regression as well.

Dodgers starting pitcher Hyun-Jin Ryu is pitching to a 1.36 ERA this season however his FIP, xFIP and SIERA are 2.62, 2.91 and 3.30, respectively. Those numbers aren’t surprising. After all, we have to expect some regression from Ryu who entered the season with a lifetime 3.20 ERA. Even if he pitches to a 3.30 ERA the rest of the season as SIERA suggests, Ryu would still be one of the best pitchers in baseball.

Brewers starting pitcher Zach Davies , seems to be everyone’s poster boy for regression. He’s pitching to a 2.41 ERA but according to FIP, xFIP and SIERA, major regression is on its way. Davies’ FIP is 4.00, xFIP is 4.83 and SIERA is 5.09. Sell high? You might be able to get a lot back in a trade when you’re offering a pitcher who is 7-0 with a 2.41 ERA.

Julio Teheran , the veteran Braves starting pitcher has a 0.81 ERA in his last eight starts. Before his Thursday start his FIP was 4.21, his xFIP was 4.83, and his SIERA was 4.84. His trade value will probably never be higher at any point this season. Do you trade him? To be continued…