Giants third baseman Pablo Sandoval enjoys a moment of quiet reflection after booting a seventh-inning grounder in Game 4 of the NLCS in St. Louis. (Jeff Haynes/Reuters)

There was a time when Tim Lincecum’s mere appearance on a mound brought a peaceful excitement to fans of the San Francisco Giants. He was an oddball, but he was their oddball. He threw baseballs by hitters and won games with such regularity it seemed to be a relationship that was just beginning, one that would prosper for years.

Thursday night, in a spot he once relished, Lincecum instead shrunk. He could not get out of the fifth inning of Game 4 of the National League Championship Series. He gave up searing liners and walked the opposing pitcher. He laid the foundation for an 8-3 loss to the St. Louis Cardinals, a loss that not only put the Giants in a dire three-games-to-one hole in the series, but continued perhaps the primary theme of their season: What to make of Tim Lincecum, now and in the future?

“I think that will be something I’ll do in the offseason on my own,” Lincecum said afterward. “I can’t really say right now what I’m going to be doing differently. I’ve still got a few months to work on that. Right now, I’m obviously upset at myself for the game today.”

To be sure, the Cardinals seized control of this series because right-hander Adam Wainwright allowed jut four hits and one run over seven innings, his curveball dancing and delighting a Busch Stadium crowd of 47,062. They won because their balanced, deep lineup produced a hit or a walk from every spot, with Jon Jay, Matt Holliday and Yadier Molina each driving in two runs.

“We expect to win,” Holliday said. “Doesn’t matter who is on the team or who’s hurt.”

But they also won because Lincecum has become one of baseball’s great mysteries, a star who has apparently lost it. He was relegated to the bullpen earlier in the series. Yet the Giants hoped somehow the old Lincecum would emerge in a critical spot, even after a season in which he went 10-15 with a 5.18 ERA, leading the NL in losses, wild pitches and earned runs allowed.

How? Why?

“In this game, sometimes we forget at times what we’re capable of, and I think those are the times when we struggle a little bit,” said Giants lefty Barry Zito, a Lincecum confidante, before Game 4. “So it’s just a matter of him remembering who he is and what he’s capable of.”

Those, though, are the central questions for Lincecum now: Who is he? And what is he capable of at this point?

“I think that’s obviously been the hardest part, because I’ve shown flashes of what I can do or what I think I should be doing,” Lincecum said. “That’s the frustrating part. When it comes down to it, it’s not about what I’ve done. I’ve got to figure out a way to do it differently now and get my outs.”

Thursday night, the first four Cardinals went like this: single from Jay, four-pitch walk to Matt Carpenter, RBI single from Holliday, and a sacrifice fly to center from Allen Craig. It took 17 pitches for Lincecum to trail 2-0, and pitching coach Dave Righetti was already visiting the mound.

“You’re just digging yourself out of a hole,” Lincecum said.

It was the beginning of an uneven performance near the end of an uneven year. For 2008 and 2009, Lincecum was the best pitcher in the NL, if not all of baseball. In winning two Cy Young awards, he went a combined 33-12 with a 2.55 ERA and 526 strikeouts, leading the league in that category both years. He won the clinching game of the 2010 World Series. He was embraced as a counterculture hero by counterculture San Francisco.

How far has he fallen? Thursday night, when he began Game 4, he opened by pitching from the stretch — with no one on base.

“At times during the course of the year, he was battling his delivery and would get out of sync occasionally,” Giants Manager Bruce Bochy said. “So just to keep it simple, he just went from the stretch, and he liked it.”

Translation: He was searching. The search continued Thursday. Slumping Hunter Pence gave the Giants some hope against Wainwright when he pounded a solo homer in the second. Lincecum then worked around an error and two walks — including one to Wainwright — in the bottom of that inning, and retired the side in order in the third and fourth.

Who, exactly, is he? Not the same guy from frame to frame, it turns out.

“Early, he . . . had trouble getting the ball where he wanted it,” Bochy said. “He settled down and actually threw the ball fairly well.”

But in the fifth, Carpenter scorched a one-out double, and Holliday scored him with a single — the key play, because catcher Hector Sanchez couldn’t corral the relay throw, which was in plenty of time. Lincecum followed with a strikeout of Craig. One more out, and he would have kept Giants in the game — and the series.

But here came Molina, the Cardinals’ catcher, at that point just 3 for 14 in the NLCS. When he bounced a ball back up the middle and into center, Lincecum didn’t leave the mound. He stared straight to the outfield as Holliday scored to put the Cardinals up 4-1.

With time called, Lincecum slowly climbed back to the top of the mound, reaching the rubber. He would not throw another pitch. Bochy eventually met him there and took the ball. His line: 4 2/3 innings, six hits, four runs, three walks, three strikeouts. His night was over. His season might well be. His career? Hard to say. We no longer know what Tim Lincecum is capable of.