Tim Lincecum needs to find his inner idiot. And do it idiotically fast.

That’s not what I say. That’s what he says.

“I’ve always been a thinker,” Lincecum admitted Sunday after the Giants’ 6-2 loss to the A’s. “Sometimes it’s just easier to go out there and do it. You know, keep it simple, stupid. Play like you’re an idiot. The way I was back in my earlier days, when I was arrogant. Maybe I need to get back to that.”

He needs to do something different. That’s for sure.

If there were doubts before, his performance at AT&T Park served as an official notice: Excessive hand-wringing over Lincecum is now permitted among Giants fans.

When he began the season slowly with some rocky starts, the common wisdom was that Lincecum would soon snap out of it. But this was his ninth start. There is still no snapping. There is only the Lincecum we saw Sunday. He goes from excellent to exit in a hurry. In this case, after just four innings.

“He looked great early,” said Giants manager Bruce Bochy, whose own hands showed signs of wringing. “But it’s a similar story. He’s having a hard time staying out of a big inning.”

More than any previous Lincecum start, however, Sunday was a major alarm-bell ringer. There’s no way he should have been knocked out so early against an A’s batting order that — because of injuries to Coco Crisp, Yoenis Cespedes and Brandon Inge — had the look of a random page from the San Leandro phone book. Only one hitter in the A’s lineup entered the game with a batting average above .240. That was Josh Reddick (.270), who also owns the second-most strikeouts on the team.

For a man of Lincecum’s talent and reputation, it should have been like shooting fish in a barrel. Instead, after he allowed just two base runners in the first three innings, Lincecum shot holes in the barrel and let the fish swim around the bases willy-nilly.

After the fourth inning was over — and Bochy pulled him after 90 pitches — Lincecum had allowed the A’s to score four runs on a messy series of singles and walks. Lincecum also endured the indignity of throwing a wild pitch that allowed Collin Cowgill to score from second base — while colliding with Lincecum, whose jaw was rocked by the top of Cowgill’s helmet on the play.

Afterward, Lincecum said there were no lasting effects from the crash except for a hyperextended thumb on his left (non-throwing) hand. But it’s never good when a pitcher begins a game with a 5.77 ERA and finishes with a 6.04 ERA.

Theories abound about Lincecum’s struggles. Here’s mine: With his renowned “freak” pitching motion, he is like a unique and sensitively-tuned foreign car that can go totally haywire with just one misfired piston — and because the Lincecum motion was developed and curated exclusively by him and his father, it’s difficult to find a repair shop to fix things.

Others go elsewhere for answers. A popular notion is that when he allows a base runner and has to pitch from the stretch, Lincecum doesn’t deliver the ball as nastily or as perfectly.

“I don’t know if he’s losing a little concentration when in the stretch or what,” Bochy said.

Lincecum says he does know — and doesn’t agree with his manager.

“No, I don’t,” Lincecum said. “I feel like I’m pretty focused. It’s a matter of being able to execute pitches.”

Another theory is that Lincecum, with his slight build, has lost the vigor on his fastball at the advanced age of 27. Yet on Sunday, he was throwing 91 mph fastballs for strikes — roughly the same speed as in his Cy Young seasons.

So is a good chunk of Lincecum’s problem mental?

“Could be,” Bochy said.

On this, Lincecum does agree. When the Giants’ locker room door opened Sunday after the game, Lincecum and catcher Buster Posey were standing in a corner, talking quietly and intensely. After the discussion broke up, Lincecum did not reveal any details. But it was clear his inconsistency is troubling to him.

For instance, he would like to do a better job of sustaining the momentum of his good one-two-three innings and keeping them rolling. Instead, Lincecum said he walks to the mound each inning with an “open mind” to face each challenge. This is why Lincecum says he wants to be more of an idiot, to just ride a wave throughout the game rather than shifting too many brain gears from hitter to hitter.

Makes sense. Lincecum’s “freak” persona has frequently obscured the fact that he’s a bright guy. He is, after all, a college man from the University of Washington. In the clubhouse, he is famous for knowing the lyrics to hundreds of songs. And thanks to his dad, he’s an expert on the physical mechanics of pitching.

It should help, Lincecum notes, that he is now a veteran who has been through other funks, from which he has always emerged eventually.

“I’m just trying to take what I’ve learned and coordinate it with the times that are going on now,” Lincecum said. “It’s not working right now; I’m not saying that it won’t work, but it’s just … there’s a time and place for everything. I’ll find a way out of this. It’s just the way it is.”

The calendar still says May. Lincecum has plenty of time to develop more internal stupidity. But there is a question that every Giants fan should fret over — and should keep fretting over until Lincecum’s funk has vanished. Here is the question:

What if he is too smart to be an idiot?

Contact Mark Purdy at mpurdy@mercurynews.com or 408-920-5092.