The key to the Giants rotation, however, and the piece that could push them unequivocally past the Los Angeles Dodgers in the National League West might be the man penciled in as the No. 5 starter.
That'd be Matt Cain, former workhorse and current enigma.
Right now, Cain is the guy who hasn't posted a sub-4.00 ERA in any of the past three seasons. He's the guy who had bone spurs removed from his elbow in 2014 and made just 11 starts last year after suffering a forearm strain in April.
On the other hand, he's still just 31. And Giants fans don't need to chase their garlic fries with ginkgo biloba to recall the run of success that made Cain one of the most consistent right-handers in the game not so long ago.
After debuting in 2005, Cain eclipsed 200 innings every season between 2007 and 2012, posting ERAs under 3.00 in three of those campaigns and making three All-Star appearances. Along the way, the Giants won a pair of their recent trio of titles, and Cain authored a perfect game for good measure.
Tim Lincecum commanded more attention with his flowing locks and unorthodox mechanics, but Cain was the backbone of San Francisco's starting five for the better part of a decade.
Now, he's in camp searching for answers and, more importantly, the results that once came so readily.
Cain said of his recent struggles, per Andrew Baggarly of the San Jose Mercury News:
I've had long nights thinking about that one. I don't know exactly what was keeping me from being consistent and making the pitches I wanted to make most of the time. I couldn't tell you if it was something physical or something mental or if the wind was blowing the wrong way. But it was something that happened a lot and it was tough to go through, and the big plan is to be able to get past that.
Plans are one thing, execution is another. Everyone is in the best shape of his life and on the right track in late February (OK, not everyone). But Cain is now far enough removed from his salad days for the questions to become darker.
Like: Can he be an elite or even effective big league pitcher ever again?
Velocity isn't the problem. In 2012, his last good season, Cain's fastball averaged 91.1 mph, per FanGraphs. Last season, his average heater clocked in at 91.0 mph, while his ERA ballooned to 5.79. His issues, in other words, might be related to rust more than stuff.
There are case studies that point toward optimism, as McCovey Chronicles' Grant Brisbee outlined:
Let's look for pitchers who came back with a second stage of their careers, then. [Ryan] Vogelsong is an outlier, but he's near and dear to our hearts. John Lackey isn't quite so near and dear, but he was the most hated pitcher in Boston when he was Cain's age. Three seasons later, he helped the Red Sox win a World Series. Three seasons after that, he picked up stray Cy Young votes. He was buried much deeper than Cain and he wasn't as good in the first place. Edinson Volquez was waiver fodder for years before being a Game 1 starter again.
Pitchers come back from all sorts of calamity.
More often, they don't. That's the wet blanket. If you're playing the odds, Cain will never again pitch like a No. 1 or anything close to it. FanGraphs projects a 4.35 ERA in 121 innings in 2016, while Steamer is a tick more optimistic, foretelling a 3.90 ERA in 130 innings.
Either one, or a split-the-difference stat line, would be perfectly palatable for a fifth starter. But what if Cain finds a way to wind back the clock? How scary would this already formidable Giants team become as it embarks on yet another even-year run?
Let's assume Cueto and Samardzija both stay healthy and get boosts from the Giants' stellar defense and pitcher-friendly park. Let's say Bumgarner once again does Bumgarner things. And let's stipulate veteran Jake Peavy has another year of effective grinding left in his arm.
If Cain kicks in anything, that's a strong rotation. And there are options behind him, including sophomore sinkerballer Chris Heston, who tossed a no-hitter last season.
But if Cain returns to All-Star level? You're talking about easily the deepest, scariest starting five west of Queens.
Pair that with San Francisco's balanced lineup littered with homegrown contributors, and Los Angeles' run of three consecutive division titles is threatened, if not doomed.
The Dodgers boast plenty of talent. They're baseball's biggest spenders, after all, and while they lost Zack Greinke to the Arizona Diamondbacks, they could fill the void with Japanese ace Kenta Maeda and the return of Hyun-Jin Ryu, who missed all of last season with a shoulder injury.
Right now, the storied bicoastal rivals are neck and neck, with those Greinke-swiping Snakes coiled in the weeds. The NL West race could well turn on a comeback performance or larger-than-expected contribution from someone.
Every team can point to at least one player who potentially fits the bill. For San Francisco, it's Cain. If he has a genuine renaissance in him, it could be bigger than any offseason addition.
The workhorse, in other words, has become the wild card. The question now is, can he be an ace?
All statistics courtesy of Baseball-Reference.com unless otherwise noted.