One who, despite winning the 2002 American League Cy Young Award and starting 7-2 this season, has won only one game in his past 14 outings.
Although it would have been magic for the Giants to clinch their first NL West title since 2003 on Saturday, Zito admitted after the game it would have been just as important from a personal standpoint for him to be the guy to deliver it.
After all, since signing a seven-year, $126 million contract prior to the 2007 season, Zito has gone 40-57 with a 4.45 ERA in orange and black.
"Yeah, of course," Zito said. "I wanted to deliver for the team. We've been battling our [butt] off here and to go out here and scuffle and not be able to do that and give ourselves a chance to win, I'm extremely disappointed in myself."
The disappointment began early -- a leadoff chopper up the middle, another single to right field, a sacrifice bunt, followed by an intentional walk to the ever-dangerous Adrian Gonzalez.
Zito got the second out, a weak popup to second base, but then twice committed the cardinal sin of pitching: two bases-loaded walks to Yorvit Torrealba and Scott Hairston that put the Giants in a 2-0 hole.
Despite those two walks, and his fourth and final one to fellow starter Tim Stauffer that prematurely ended his day in the fourth inning, Giants catcher Buster Posey said Zito's overall command wasn't bad.
"He did a good job getting a pop fly, really made a pretty good pitch," Posey said. "I don't think he was pitching too far away from contact there to Torrealba."
The main issue, Zito said, was his fastball location. As a soft tosser, Zito must effectively place his mid-to-high 80s fastball in order to set up his changeup and patented hook.
When that's working, he's on. When it's not, pitching lines such as Saturday's -- three-plus innings, four runs (three earned) on five hits and four walks -- show up in the box score.
"It looked like he was getting out of that inning," Giants manger Bruce Bochy said of the first. "A couple walks hurt him and his pitch count got up there, but he was off. He wasn't getting the ball where he wanted. He was battling out there."
Another subpar outing by Zito brings about an interesting dilemma. Should the Giants advance to the playoffs -- which can happen with a win Sunday or through a host of tiebreaking scenarios -- will Zito be a part of the playoff rotation?
It's a question San Francisco will most likely ponder. On one hand, Zito's the only starter with a postseason background -- and a good one at that, going 4-3 with a 3.25 ERA in seven starts.
On the other, outings such as Saturday's are fresh in the Giants' mind. And should fellow starter Jonathan Sanchez rise to the occasion on Sunday in the biggest game of his career and pitch the Giants into the postseason, he or ultra-competitive rookie Madison Bumgarner could possibly be given a serious look.
A valid question, yes. But also one that can't be answered -- and doesn't warrant too much consideration -- until a playoff spot is secure.
After two straight losses, the champagne bottles remain on ice. Matt Cain could have started off the weekend with a party on Friday. On Saturday, Zito could have stepped up and been the big-game pitcher he was expected to be.
Instead, like too many times during the past four years, he wasn't.
"Coming into the series, we knew we had to take one, and now it's coming down to the last game," Zito said. "Unfortunately, I couldn't put it away."