Matt Cain was rocked for seven runs in a 2 1/3-inning stint that was his shortest of 135 Major League starts, and the D-backs went on to hang a 10-8 defeat on the Giants that dropped them five games behind Colorado in the National League Wild Card race, with 11 games remaining.
"It was pretty bad. I kept making mistakes over and over," said Cain, who remained with one win in 10 starts since late July. "In the past couple of starts, it was a bad pitch here and there. Today, there were a lot of them."
They added up to a startling sight for a team accustomed to seeing the 24-year-old dominate and at the very least compete.
"We had the right guy out there, the way he has been pitching all year," Bochy said. When things went south for Cain, "the hitters were fighting to pick him up."
But the Giants couldn't mount a matching offensive against Arizona left-hander Doug Davis (8-13), who scattered 10 hits and allowed five runs in 7 1/3 innings.
As they say, the game wasn't as close as the score indicated: Pablo Sandoval tightened the final by drilling a two-run triple in the ninth and scoring on pinch-hitter Randy Winn's sacrifice fly.
The outing by Cain (13-7) completed a disastrous spin for the Giants' rotation. In the last five games, encompassing the current road trip, Giants starters have totaled 17 2/3 innings.
"You expect them to stumble once in a while. ... It just so happened that they all did once around the rotation," Bochy said.
"It's been bad," Cain said. "That's not what we all wanted to do. We like to challenge and push each other, and I feel like I let a lot of people down."
Cain, already owning a quick 1-0 lead, breezed through a one-two-three first inning. Then came the nightmare, one of those bad dreams from which you cannot wake up.
He faced 12 more men. Eight of them reached base. Seven of them scored.
His rut was so deep, not even the reversal of a home run call could help. In the third, Miguel Montero had already given the D-backs a 5-4 edge when Gerardo Parra's drive to right-center was initially ruled a two-run home run.
Led by center fielder Aaron Rowand, the Giants protested the umpires into a video replay. Their conclusion was that Parra's drive had rattled around the 413-foot sign without ever clearing the wall. Double.
No matter. Montero still got to score on that play, and Brandon Allen's single eventually delivered Parra, too.
"He just left a lot of balls over the plate," said Arizona third baseman Mark Reynolds, whose contribution to the barrage was a run-scoring single for his 100th RBI (Reynolds also fanned three times, to hike own Major League record of 204 strikeouts, set last season, to 206).
"If you go look at all of our hits," Reynolds added, "they're catching a lot of white and normally he's on the corners with his fastball and sliders, but tonight he left a lot of balls over the plate and we put a good swing on them."
Cain has had a poorer start -- he allowed nine runs to the Cardinals on April 18, 2008 -- but he had never had a shorter one without injury being a factor. He left his July 11 start against San Diego after 1 2/3 innings when struck on the forearm by a line drive.
Cain delivered the game's first big offensive blow, following a two-out walk of Kevin Frandsen in the second inning with a two-run triple. Cain's first three-bagger in 249 career at-bats gave himself a 3-0 lead.
His undoing immediately ensued -- but both he and his manager waved off the notion that he could have left his best stuff on the basepaths.
"Not at all," Cain said, shaking his head. "I was just not able to locate the ball. I was leaving a lot of stuff up."
"Did the triple take a lot out of him? That's a hard one to answer," Bochy said, "but he's in as good a shape as any of our players.
"These guys," Bochy signed off, "are allowed to have an off day. They've done too good a job."
The game received a charge of electricity in the seventh inning, when onetime D-backs icon Randy Johnson strode in from the bullpen to a warm reception from the 25,591 fans.
He surrendered a solo homer to Rusty Ryal for the D-backs' final run -- around which he did strike out the side.
Johnson was making his second relief appearance since being activated after more than two months on the DL with a slight rotator cuff tear. Johnson's first appearance had come Saturday in Los Angeles, with the Giants trailing, 9-1. Tuesday night, he relieved with the Giants down, 9-4.
That probably isn't the mop-up role the club envisioned for the 46-year-old 303-game winner when the decision was made to activate him for bullpen help.
Then again, the Giants couldn't envision this ragged stretch by their five-star rotation, either.