Cain isn’t able

The human impulse is to be patient with Matt Cain, knowing what he has meant to the Giants in their championship era, remembering the precious scene with his wife after his perfect game. Yet halfway through an erratic season for baseball’s reigning champions, the competitive reality is decidedly harsher.

It goes: No way will this team reach the postseason if he’s expected to be the No. 2 starting pitcher.

While no permanent judgments should be made after his 2015 debut, Cain’s rocky loss Thursday in Miami doesn’t jibe with management’s hopes that he’ll regain his three-time All-Star form. He struggled with his command, then collapsed in a four-run fifth inning in which he was torched by two home runs, including a three-run shot by the same Justin Bour who buried Santiago Casilla with a three-run walkoff homer the night before. The Giants lost 5-4, and after being swept by the Marlins, they’re only four games above .500 as they head to Washington, where the only good thing about playing the Nationals three times is that they avoid the world’s hottest pitcher, Max Scherzer.

As is the Giants Way, all was positive after Cain’s outing. The 30-year-old right-hander was pleased to report no pain after his first start since last July 9, when an elbow injury ended his season, required surgery and led to other injury woes.

“It was probably one of the better days I’ve had feeling-wise, which is really a big positive,” Cain told reporters. “It’s just now ironing it out and making good pitches. … The ball feels a lot better coming out of my hand.”

Yet compared to his partner in return-from-rehab drama — Miami’s Jose Fernandez, whose own season debut was successful and filled with impressive breaking stuff and fastballs in his return from Tommy John surgery — Cain’s heat topped out in the 91-mph range. Fernandez also touched Cain for a solo homer, a shot that ripped over the left-field fence like a speeder on I-95. “If that progresses with getting more innings, that’s great,” Cain said. “It feels comfortable now. It’s just about making good pitches.”

Bruce Bochy, too, emphasized restraint in allowing Cain to reacclimate. “I think he should be encouraged,” said the Giants manager, always supportive. “His first four innings, I thought he was pretty good. He’s going to get better, building up his strength and stamina. He looks healthy, I’ll say that.”

Still, what is the end game here? Is it to make Cain a serviceable starter so the front office can feel better about a $127.5 million contract that has two full seasons remaining and a vesting option for 2018? Or is to try and win the World Series for the fourth time in six years, which currently looks like a pipedream?

With the trade deadline approaching, the Giants’ celebrated braintrust has stubbornly advanced a curious theory: An array of veteran arms can carry the rotation load behind Madison Bumgarner by, in effect, competing against one another. But as Brian Sabean, Bobby Evans and Bochy know better than anyone, dominant pitching wins in the playoffs; the teams with the most potent and reliable front-end arms have the best chance of winning banners. The Giants can’t expect another Bumgarner-as-Paul-Bunyan show in August and September, and as Cain returns from elbow and ankle problems, you can’t simply slot him at No. 2 and expect miracles. Truth be told, no one behind Bumgarner is a sure thing. Chris Heston and Ryan Vogelsong have had their fine moments, but the injured Tim Lincecum and soon-to-be-40 Tim Hudson — away from the club to take care of personal matters — are major question marks. As for Jake Peavy, he tries to squeeze what he can from an aging body starting tonight, when he returns from back problems that have sidelined him since early April.

Honestly, is this the kind of piecemeal rotation you want competing against the Nationals, Dodgers and Cardinals?

If the Dodgers didn’t have their own issues and if Bud Selig hadn’t approved a two-wild-card system late in his commissionership, the Giants already might be dismissing 2015 as the dreaded odd-numbered year. They went 12-14 in June after an ugly April. But the Dodgers went 15-15 with a feeble offense, Yasiel Puig in zombie mode and a rotation with its own issues, even with Clayton Kershaw and Zack Greinke. If the Giants want to make a charge at a playoff berth, they have a decent chance assuming Hunter Pence stays healthy when he returns after the All-Star break.

But they will need a No. 2 starter. And this is where the braintrust — from CEO Larry Baer on down — must reach down and decide how dearly they want to win again. The Giants owe it to their fans, who continue to sell out every game, to pursue an intimidating arm to place behind Bumgarner and let Heston, Cain and the others decide who are the Nos. 3, 4 and 5. In a previous piece, I’ve mentioned Cincinnati’s dazzling Johnny Cueto, who pitched a gem the other night and is ready to be a three-month rental before hitting free agency. Others have suggested another Reds starter, Mike Leake, but he’s no Cueto. If Cole Hamels doesn’t fit the Giants’ price point, Scott Kazmir certainly would across the Bay.

This time, the Sabean administration can’t just sneak up and acquire another Marco Scutaro or Cody Ross. The boys have to think bigger this time. They’ve said one reason they don’t want to acquire another starter is because they don’t want to shove aside Lincecum in what likely is his swan song in San Francisco.

Gentlemen, this is big business.

We’d all like to see Cain, Lincecum and Peavy thrive again. They’re great human stories. “You get it taken away from you for an amount of time, whatever that time is, you definitely learn to appreciate it,” Cain said. “It’s supposed to be fun.”

Winning in October is even more fun.

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