The A's rotation with Luis Severino

After signing with the A's on a three-year, $67 million deal that includes an opt-out after two years, Severino will be the official ace of the staff heading into 2025. Last year, in his first full season since 2018, Sevvy held a 3.91 ERA (4.21 FIP) across 182 innings with a 1.24 WHIP.

His experience in the big leagues, ability to get ground balls, and his upside as a starter that can hold a 3.50 ERA or better all make him the logical choice to be the ace of the staff this coming year. The hope is that with his addition, the young arms in the rotation will have a veteran to lean on throughout the course of the season.

It also won't hurt to have someone in there that can reliably go deep into games and save the bullpen every fifth day.

JP Sears

Sears has been a solid starter for the A's the past two seasons, making a full slate of starts in both 2023 and 2024 while providing league average results. Last season he made some modest improvements, tossing a few more innings, lowering his home run allowed rate, and his ERA.

He finished the year with a 4.38 ERA (4.71 FIP), just above league average, over 180 2/3 innings. That was just over eight innings more than the previous season over the same number of starts, which means he was going deeper into games. That will be a recurring theme for the A's as they look to return to contention. They'll need guys that can go at least five-plus innings on a consistent basis.

Mitch Spence

Spence was the A's Rule 5 selection at right about this time last year, and after starting the season in the bullpen, he was quickly thrust into action in the rotation as the injuries began to mount. His progress wasn't a straight line pointed upwards, with some growing pains along the way, but he did improve a little bit in the second half of the year, posting a 4.37 ERA across 68 innings, though his FIP was exactly the same in each half at 4.21.

Spence finished the year with a 4.58 ERA (4.21 FIP) across 151 1/3 innings, and held a 48.4% ground ball rate, which could be a useful skill to have as the A's head to Sacramento where the ball tends to travel a bit more than at the Oakland Coliseum.

Spence is a strike thrower, which is another attribute, along with accumulating innings, that A's manager Mark Kotsay has been targeting from his pitchers. The team's improvement in those two facets of the game in 2024 helped lead them to a 19-win improvement over the 2023 campaign.

Joey Estes

Estes is the final piece of the rotation that could be considered a frontrunner for a spot to start the season, after having some brilliant performances over the course of the '24 campaign. He made his MLB debut in 2023, getting two starts down the stretch, before making himself a regular in the rotation in May of 2024.

The 23-year-old righty made 24 starts this past season, holding a 5.01 ERA (4.94 FIP) over 127 2/3 innings. While his 16.9% strikeout rate was a bit below league average, his 5% walk rate was superb, and led to him holding a 1.23 WHIP in his first full season.

One worrisome note on Estes is that his ground ball rate was the lowest on the club at 24.6%. The A's have been targeting ground ball pitchers with their acquisitions thus far this winter, and nearly all of them have had a GB% above 50%. Severino is one exception at 46%, though his years of experience should help bridge that gap.

If you were to ask, a lot of the people that have watched Estes regularly would say that he has the stuff to be the future ace of the club, and it's likely he'll be given a chance to grow into the role even more in 2025.

J.T. Ginn

Just a couple of weeks ago, we mentioned J.T. Ginn potentially having an inside track for the fifth spot in the A's rotation due to his ground ball rate. In eight games with the Athletics, Ginn's GB% sat at 47.1%, which was the second-highest of any starter still with the club, only behind Spence. That was also the first time in Ginn's pro career that his ground ball rate dipped below 50%.

In an interview on A's Cast following the Severino signing, Kotsay mentioned five starters, and Ginn was one of the five that he named, suggesting that he is firmly in the mix to begin the season in Sacramento.

In eight appearances (six starts) with the A's in 2024, Ginn held a 4.24 ERA (3.96 FIP) and also held an impressive 6.3% walk rate, which was a little bit lower than he'd had in the minor leagues, but he'd consistently finished between 7-9%.

GInn could be a sleeper in the A's rotation that starts off as the No. 5 starter, but finishes the year as more of a middle-of-the-rotation guy.