What the SF Giants see in new starting pitcher Sean Manaea

A talented-but-troubled pitcher that's been on the SF Giants' radar for years finally makes his way (back) to the Bay Area.

It was not Justin Verlander, or Jacob deGrom. Kodai Senga signed with the Mets, and Taijuan Walker became a Phillie. Masataka Yoshida didn't sign with the Giants, and neither did Jameson Taillon. Carlos Rodón's time in San Francisco is already over. No, the big starting pitching acquisition for the SF Giants this offseason was southpaw Sean Manaea.

Kyle Ross-USA TODAY Sports

San Francisco signed Manaea to their signature "two years with a player opt-out after one year" contract, this time at $12.5 million per. Like with Rodón, the Giants hope to polish up Manaea and squeeze a career year out of him before he seeks a larger contract elsewhere.

Unlike Rodón, though, Manaea has never really had a dominant season. Sure, he posted a great 5-game sample in 2019 after recovering from shoulder surgery (1.21 ERA in 29.2 IP), but his best season other than that was probably 2018 when he tossed 160 innings of 3.59 ERA ball. Would that be a welcome addition to a potentially thin rotation? Certainly. But it also seems like a way to replace Rodón and DeSclafani's production last year (great and basically nonexistent, respectively) with Manaea and DeSclafani's production this year. Replacing one great player with two good™️ ones certainly has its risks. In that sense, Manaea represents a proof of concept that I'm surprised the Giants are investing in.

That's because the only way this signing really works is if they make Manaea better than he ever has been. And that's a steep hill to start climbing. Last year, Manaea pitched 158 innings, just about a full load for a starting pitcher in 2022. He was worth negative WAR, and not just barely - he posted nearly a full win below replacement, becoming one of five pitchers in the majors who did so despite throwing at least 150 innings. Still, Manaea was much better than that in 2021, before his trade to San Diego. On average, he's been worth two and a half wins per full season. The question becomes, how do the Giants undo whatever it was that happened to him last season?

That starts with helping Manaea regain his command. He's never been a below-average pitcher in that regard, but he's posted some impressive seasons in the recent past, including a 2020 in which he walked just 3.6% of batters he faced. Last year, though, that number more than doubled, to 7.5%. He's done the best when he's limited walks, which is true of most pitchers not named Brian Wilson or Ryan Vogelsong, but it's especially salient that Manaea's best seasons have come when his walk rate has remained under 5%.

There's also the chance that Oracle Park helps with the other half of the Giants' go-to pitching equation - limiting home runs. Per Statcast, 7 of the 30 home runs Manaea allowed last year would have stayed in the park at Oracle, even with the drawn-in center field wall. Petco Park and Dodger Stadium both would have held in a few of his allowed home runs as well, which is significant considering how important those matchups will be.

Perhaps most importantly, Manaea might benefit from an Alex Wood-type management plan, where he's set up to take advantage of prominent career splits. Manaea excels against lefties, posting a career .601 OPS against, compared to a .752 OPS against righties. Last year, these figures were even more prominent. Manaea limited lefties to a .599 OPS but got lit up to the tune of an .815 OPS against right-handed batters. Even when he's struggled, Manaea's been a fantastic option against the left side.

Still, if the Giants believe they can polish up Manaea to the point of being a legitimate third-starter with second-starter potential, they must determine how to unlock his strengths even as they attempt to mitigate his weaknesses. Fortunately for Manaea, the Giants have a pretty good track record with pitchers like him. Manaea's primarily a sinker-changeup guy, and the Giants have made sinker-heavy pitchers like Kevin Gausman, Logan Webb, and Alex Cobb look really good in the recent past. It also helps that Manaea has shown elite movement with his changeup, too.

Sean Manaea Changeup, Vertical Movement (inches) vs. Average

2016: 7.6

2017: 8.1* 

2018: 7.2* 

2019: 5.6

2020: 4.6

2021: 0.7

2022: -1.2

*Top 3 in MLB (Qualifying Pitchers)
Data per Baseball Savant

The Giants have to think they can tap into something from his past to help him regain that elite vertical movement in his changeup, although they might be fighting a battle against time. Whether it's the lingering effects of his 2018 shoulder surgery, or simply the Padres desperately throwing mechanical tweaks at the wall to see what sticks, Manaea's changeup has steadily gone from elite to ordinary. Even if the Giants get Manaea's sinker working to a satisfactory degree, that changeup may be the difference between him eating innings in the back of the rotation and him anchoring the middle of a potential playoff rotation.

Ultimately, Manaea won't make or break the Giants' 2023 season - or at least, it shouldn't. Fans should rightfully be concerned and at least a little irritated that the Giants haven't made moves to secure superstar talent thus far this offseason (and it's hard to see one left to acquire). But in a vacuum, Manaea makes sense. He's a relatively inexpensive gamble on the Giants' ability to do something they've proven they can do well, albeit with a significantly murkier ceiling. In the best case, Manaea and Cobb end the season battling for the role of #2 starter behind Webb with ERAs a tick above 3.00. Worst-case scenario, Manaea ends up as an expensive long-relief option. In the likeliest case, Manaea ends up adequately covering innings in the back end of the rotation.

Actually, I take it back. The best case is that the Giants signing Carlos Rodón and Kevin Gausman to long-term deals and solidifying an elite top-three atop the rotation, and Manaea makes the entire league complain about how unfair it is that the Giants always get everything. But you can't win a World Series looking backward. Welcome to the SF Giants, Sean Manaea.