Last season was a great one for the A's bullpen. Heading into the 2019 season, what will their starting five look like, and how well should fans expect them to perform?

The 2018 Oakland Athletics sported one of the best bullpens in baseball. In fact, the relief squad ranked second in the American League in earned run average (3.37), innings pitched (641.1), WHIP (1.18), and batting average against (.220). This group cleaned up masterfully for their underwhelmingly average starting rotation. So what comes next?

According to, Oakland Athletics manager Bob Melvin has already settled on four of five starters. Behind their Opening Day starter, Michael Fiers, the A's will feature Marco Estrada, Brett Anderson, and Daniel Mengden. Three of the four are returning Athletics starters from last season, with Estrada being the lone outlier (a Blue Jay in 2018). All also happen to be well-seasoned MLB vets, with the exception of Daniel Mengden. All signs point to their effectiveness as a group being a significant question mark:

Michael Fiers

The 33-year-old had a resurgent 2018 season, during which he posted a 12-8 record, 3.56 ERA, and 1.18 WHIP, through 172 innings. He did so, splitting time between the A's and the Detroit Tigers, due to an August trade between the two American League ball clubs. Bob Melvin, the A's organization, and the fans will have to hope that the '18 magic hasn't worn off, though, as Fiers' career numbers suggest the aging righty will come back down to earth, to a certain extent: 894 IP, 54-55 record, 4.04 ERA, 1.27 WHIP.

Marco Estrada

The former Toronto Blue Jay may be the biggest question mark in the A's starting rotation. That is, of course, besides the purported open fifth starter spot. The 35-year-old is coming off his worst season, as a full-time starter, in his career. During the 2018 campaign, he posted a 7-14 record, 5.64 ERA, and 1.43 WHIP over 143.2 innings. This, also, coming off of an already woefully-subpar '17 effort in which he yielded an earned run average of (4.98).

Brett Anderson

The 31-year-old southpaw, in short, does not appear to be poised for a breakout 2019 campaign. Through 80.1 innings, over 17 starts in 2018, Anderson posted a 4.48 ERA, with an alarming batting average against of .285 and an a 1.28 WHIP. Endurance may be the biggest concern for Brett and the A's, however, as he has only topped 100 innings once (180.1 in 2015) over the past eight seasons. Another year of heavy bullpen work seems to be in store, should the A's brass be interested in Anderson's '19 longevity.

Daniel Mengden

Mengden likely has the most potential for improvement, possibly even a breakout year. By far the youngest of the starting four, the 26-year-old has pitched parts of three seasons for the big league club. Last season being the most work the youngster has experienced in Oakland, the organization and fans, alike, were given the opportunity to see what Mengden had to offer. He responded, putting up a 4.05 ERA and 1.12 WHIP over 115.2 innings. He even mixed in a complete-game shutout. With the backing of a strong bullpen, Bob Melvin's expert handling of his staff, and a solid '18 effort under his belt, Mengden should continue to progress and prove fruitful for the Oakland faithful.

With the season fast-approaching, Melvin will have to use the remaining exhibition games as a winner-takes-all audition for the final starter's role. The odds-on favorite, at this point, has to be the former third-round pick, Frankie Montas. After turning in a solid '18 effort, with a 3.88 ERA over 11 starts (65 IP), Montas has gotten off to a hot start down in Arizona: 3 games/2 starts, 9 IP, 1.00 ERA, 1.22 WHIP, 8 strikeouts. Assuming he doesn't tank his final Spring Training outings, Montas should be an unavoidably attractive option to pencil-in as the fifth starter. His youth would be a welcome sight for the mostly-over-30 group of starters, though, his production will be counted on to continue from 2018. All in all, one thing Oakland A's fans can surely hang their proverbial hats on is the return of their dominant core of bullpen studs.

Only time will tell how much and how often Bob Melvin will have to lean upon his star relievers.

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