Is Matt Chapman single-handedly propelling the team to greatne s on the back of his historically great defense and superb hitting? Is Khris Davis crushing? Has Sean Manaea evolved into an elite starter? Yes, yes and yes.Perhaps the biggest factor in the Athletics succe s, though, is their bullpen, which has been among the best in baseball.Over the past 30 days, Oakland's relievers rank first in Pooka Williams Jr. Jersey ERA, second in FIP, first in fWAR and fourth in strikeouts. Its generally believed that superb bullpens can help teams outperform their Pythagorean differentials; given that the Athletics Pythagorean record is just 66-53 while their real record sits at 71-48, its not hyperbole to say that their 'pen has catapulted them into the AL wild-card (and AL West) race.MORE: After some ups and downs with the Nationals, including a disappointing 6.11 ERA through June, BlakeTreinen found himself in Oakland last season as part of the trade that sent Sean Doolittle and Ryan Madson to Washington. Treinen turned it on down the stretch, pitching to a 2.01 ERA with 13 saves Trey Hill Jersey from July to the end of the season as he fine-tuned his devastating slider/sinker combo.Blake "The Witch" Treinen, 2 Pitch Sequence Sorcery (97mph Sinker & 87mph Slider). Rob Friedman (@PitchingNinja) Treinen leads all qualified relievers in ERA, is tied for the lead in fWAR and ranks second in FIP and HR/9. Treinens slider and sinker have swing-and-mi s rates of 29.8 percentand 15.6 percent (perBaseball Savant), the fourth-best and best figures, respectively, in the majors among pitchers who have thrown at least 200 of either pitch. Only Josh Hader and Edwin Diaz have higher swinging strike rates than Treinen,according to FanGraphs.That said, one C.J. Uzomah Jersey man is not a bullpen. Rookie Lou Trivino has been a superb setup option, posting the fourth-best ERA by a rookie reliever this millennium (minimum 55 innings pitched). Trivino has been the beneficiary of some generous sequencing only Kelvin Herrera and Collin McHugh have a higher LOB percentagethan Trivinos 92 percent figure;extremely high figures like those are usually subject to regre sion.MORE: But the Athletics' 'pen has been especially great thanks to recent acquisitions Jeurys Familia, Fernando Rodney Darius Hodge Jersey and Shawn Kelley. Familia profiles as a top-tier reliever; he was a dominant closer for the Mets and helped them to a pennant run in 2015, while Rodney (25 saves) closed for the Twins and Kelley was a serviceable middle relieverfor the Nationals this season.We've seen other teams take similar approaches in acquiring top-tier relievers for the postseason: Scotty Washington Jersey the Cubs and Indians acquired Aroldis Champman and Andrew Miller, respectively, in 2016, and the Yankees signed Chapman to the largest contract for a relief pitcher prior to the 2017 season. All of these moves were madeto supplement already strong bullpens. All of these teams made deep runs in the postseason as they relied heavily on their relievers.The latest baseball trendis to lean heavily on the bullpen in the postseason relievers recently have been throwing an increasing number of innings in the postseason compared to previous seasons. Its not hyperbole to say it's po sible that relievers will throw a majority of the innings in this year's postseason. By reinforcing their bullpen at all levels,the Athletics have the depth to Cam Sample Jersey pitch in the postseason like a modern team without having to worry much about fatigue (a problem that appeared to plague the aforementioned Yankees, Cubs, and Indians).Of course, the Athletics must first reach the postseason though they're currently sitting in a playoff spot, a berth is far from guaranteed in thewild West. With that bullpen on their side, however, they might just have an edge over their competitors.