SAN FRANCISCO -- Matt Cain's perfect game, the rest of the pitching staff's four consecutive shutouts in late June and Melky Cabrera's revision of the franchise's record book suggest that the Giants are charmed and striding toward the postseason.

The Giants' poor clutch hitting, their defensive woes that tend to reappear inconveniently and Tim Lincecum's yearlong struggles are symptoms of a team that's destined to stall in September, if not earlier.

Club breakdowns
First-half highlights

Which set of characteristics will take root as the Giants approach the season's most crucial juncture?

Overall, the Giants appear solid enough to remain contenders. But their streakiness indicates that an uneven ride awaits them -- and there's no telling how it will end.

Unless the offense jells, the pitching becomes completely airtight or general manager Brian Sabean finds a valuable performer or two before the July 31 Trade Deadline, the Giants won't pull away in the National League West race and instead will face a skirmish with the Dodgers and D-backs for the division title. And half the league, including the Giants, likely will scramble for the two Wild Card spots until Game 162.

"We don't expect anyone to hand anything to us," right-hander Sergio Romo said. "The Diamondbacks are in the position we were prior to us being in first place. The Dodgers are already trying to make moves."

Romo was referencing Los Angeles' attempt to obtain Houston first baseman Carlos Lee, who ended up being traded to the Marlins.

Though Sabean almost surely will attempt to strengthen the roster, as he has done each summer since the Giants became a perennial postseason threat in 2009, pitching will continue to define the club. Indeed, the rotation's fluctuations account for much of San Francisco's inconsistency -- demonstrated by a 6-1 surge from June 22-28 that put the Giants in first place, yet preceded five losses in six games.

First-half awards
MVP: MELKY CABRERA Because of him, San Francisco's offense is at least respectable.
Cy Young: MATT CAIN Madison Bumgarner and Ryan Vogelsong have excelled, but how do you deny a perfect game?
Rookie: HECTOR SANCHEZ At the rate he's improving, S.F. must find a way to keep him in the lineup.
Top reliever: SANTIAGO CASILLA Giants could have collapsed after losing Brian Wilson, but Casilla made sure they didn't.

Cain, Madison Bumgarner and Ryan Vogelsong could amass at least 15 wins each, a feat no Giants trio has accomplished since 1962, when Jack Sanford (24-7), Billy O'Dell (19-14), Juan Marichal (18-11) and Billy Pierce (16-6) excelled.

But the Giants also have endured Lincecum's well-documented ineffectiveness and Barry Zito's erratic performances. San Francisco obviously won't win every game that Cain, Bumgarner and Vogelsong start, so Lincecum or Zito, if not both, must contribute to sustain the club's hopes.

Zito (7-6) has actually pitched adequately, given his sub-.500 finishes in each of his previous five Giants seasons. Meanwhile, Lincecum's fall from his perch as a two-time NL Cy Young Award winner has been as perplexing as it is precipitous. Though his velocity has declined, he retains the ability to fool hitters, shown by his 104 strikeouts in 96 2/3 innings. The Giants, who are 4-14 when Lincecum starts, maintain utmost faith in him, and he believes that his next decent outing could propel him forward.

"We talk about momentum a lot, carrying a good outing to progressively better ones," said Lincecum (3-10).

Former Giant Mark DeRosa, now a utility man on the Washington Nationals, cautioned Lincecum's skeptics.

Players to watch in second half
BUSTER POSEY The farther removed he is from his injury and the more he plays, the better he should hit.
TIM LINCECUM Can he even come close to regaining his winning form?
PABLO SANDOVAL He must regain his power for the Giants to establish themselves offensively down the stretch.

"I wouldn't bet against him," DeRosa said. "He's the type of guy who can string together eight, nine, 10 wins in a row in the second half. They're basically in first place without him getting hot for them yet. If he does, what a boost for them."

The Giants also could use a boost offensively. Their .261 team batting average is the NL's fifth best, yet they rank 12th in scoring with 338 runs. That reflects their shortcomings at the plate with men on base. San Francisco is batting .225 with runners in scoring position, nearly 30 points below the Major League average. The Giants' average sinks to an NL-worst .183 with runners in scoring position and two outs. That's more than 50 points short of the Major League average. Both figures explain why, according to baseball statistician Bill Chuck of Billy-Ball.com, San Francisco has scored a Major League-low 100 runs with two outs.

During certain stretches this year, San Francisco's top six hitters in the batting order -- Gregor Blanco, Ryan Theriot, Cabrera, Buster Posey, Pablo Sandoval and Angel Pagan -- have generated adequate offense. But Blanco (.194 in his last 25 games) and Pagan (.192 in 24 games) have slumped lately, and Sandoval has three homers in 27 games since returning from the disabled list after recovering from his fractured left hamate bone.

Though the Giants can be expected to explore trading for a productive hitter, they already possess capable personnel. Each player simply must contribute a little more. It doesn't have to be on a record-setting scale, like Cabrera's 51-hit May that tied a San Francisco-era franchise record for most hits in a month.

Consider the 2010 season.

The Giants hit 80 homers after the All-Star break that year, tying them for the NL lead. They didn't add any impact power hitters; Jose Guillen and Cody Ross hit only three regular-season homers each after arriving in August. Nor did their scoring skyrocket. San Francisco averaged 4.4 runs before the break and 4.1 runs afterward. But this quick-strike capability helped win games.

Consider three examples: July 31, when Pat Burrell's two-out, two-run homer in the eighth inning erased Los Angeles' 1-0 lead; Sept. 4 at Los Angeles, when the Giants trailed 4-0 through six innings before Posey homered in the seventh, Edgar Renteria and Burrell went deep in the eighth and Juan Uribe added a two-run homer in the ninth; and Sept. 21 at Chicago, when Posey homered for the game's lone run.

Given the Giants' paltry total of 51 homers, which is tied for last in the NL, they'd be challenged to muster this kind of power. They are, however, a more athletic group than their predecessors. Cabrera, Pagan, Blanco, Theriot and Brandon Crawford can capitalize on their speed and gap-to-gap hitting ability.

"They're playing to their ballpark," DeRosa said.

Ultimately, they must play to their capabilities to fulfill their postseason dreams.