SAN FRANCISCO -- In the second inning of the Giants' 7-2 loss on Wednesday afternoon, an important sequence of events occurred that could be viewed as a microcosm of the team's season.

With Giants runners on the corners and one out, San Francisco manager Bruce Bochy knew the team had a possible scoring opportunity. But Barry Zito was coming up to bat, and he'd already allowed five runs on five hits and four walks.

Zito was pulled for pinch-hitter Brian Horwitz, a rookie who struck out swinging.

The staff ace was chased after just six outs -- his shortest outing of the season -- and a newcomer made an out in part because he felt pressure to get a momentum-changing hit.

The Giants managed to score a run on Tigers starter Armando Galarraga's wild pitch, but the potential rally was squashed.

"Baseball is all about momentum," Zito said. "When the team goes out, they know that they're down by three or four, things are just a little different."

And so it has been for the Giants (31-42) in 2008. For all the work Zito's done to clean up his mechanics and find the pitching prowess he once had in Oakland, he has been the weak link in the starting rotation all year. The Opening Day starter has more losses than any other pitcher in the Major Leagues.

"The difference between good players and the average players," Zito said, "are the ones that are consistent at being at their best. It just feels terrible to let the team down."

"You can't get down, you have to stay in a positive frame of mind," Aaron Rowand added. "I think he knows that everyone here is behind him.

"It's a veteran lineup that they have in Detroit. They did a good job laying off some of the pitches that a lot of the times guys swing at and get themselves out."

The Giants have now lost seven of their past eight games at AT&T Park. They've dropped their past six home series and lost three consecutive series overall. In the supposed comfort of home, Zito is 0-7. On Wednesday, in front of 38,194 fans, he retired his first batter, but the next five Tigers reached base en route to two early runs. Detroit scored three more in the next frame.

Zito opened the second by walking Galarraga on a 3-2 count. Billy Sadler began warming up in the bullpen a few minutes later. Home-plate umpire Jerry Crawford's smallish strike zone didn't help Zito's cause, but hanging pitches and a lack of control were the biggest culprits.

"Pitching at home has been more of a challenge than on the road this year, of course," Zito (2-11) said. "You got all your home fans, and they're frustrated; you want to show them a good game."

After skipping a start in early May to regroup mentally, Zito made five consecutive solid starts from May 7-29. He allowed 11 runs in 28 1/3 innings.

But he's allowed 17 earned runs in his past four appearances. His demeanor in the clubhouse remains upbeat, and he dutifully answers reporters' questions after each loss, but he seems to labor every time he gets to the mound.

Bochy said he and pitching coach Dave Righetti hadn't talked about skipping one of Zito's starts, but the team does have two off-days -- Thursday and Monday -- with which to make adjustments to the rotation.

Of missing a start, Zito said: "That's out of my control right now. I just got to focus on what I can control. I can control bouncing back tomorrow."

Local media outlets reported on Tuesday that pitching coach Rick Peterson is being considered as a special instructor to help Zito regain his old form. Peterson, let go by the Mets early Tuesday morning, worked with Zito in Oakland for three years. Under Peterson's direction, Zito was 47-17, had a 3.04 ERA and won the 2002 American League Cy Young Award.

But multiple players doubt that hiring Peterson would have any direct positive effect. One player said he doesn't think there's anything in particular a coach could say that would help turn a "magic switch."

A scout spoke highly of Peterson's knowledge -- "Give him time and he could analyze a telephone pole" -- but said he thinks Zito's problems might be related more to an arm injury than anything else.

"He just got some balls up and, to put it simply, he just wasn't sharp," Bochy said of Zito's performance. "You have got to stay optimistic, and Barry does, too."

In an attempt to clean up Zito's subpar start, Sadler, Alex Hinshaw, Jack Taschner, Keiichi Yabu and Vinnie Chulk performed admirably in seven innings of two-run relief. They allowed just five hits, but Detroit's early offensive explosion proved to be too much to overcome.

Galarraga (7-2) didn't make things easy, allowing just two runs (neither earned) in six innings of work. He scattered seven hits and two walks while striking out five. He leads all AL rookies in wins with seven, and is now 5-1 with a 2.40 ERA on the road.

"He had good stuff," Rowand said. "We just didn't get the hits in the situations we need to get hits in."

A shutout was avoided thanks to two Detroit (34-38) errors -- Travis Denker scored on a Galarraga's wild pitch, and Steve Holm reached home on Carlos Guillen's throwing error.

Meanwhile, Placido Polanco remained on a tear, extending a 10-game hitting streak by going 4-for-4 with two RBIs and a double.

For the Giants, Bengie Molina was the only player with multiple hits. He lashed a pair of singles and is now 5-for-10 in his last three games. After an 0-for-15 mini-slump, Molina has raised his average to .323, tops among all National League catchers.