It gets worse.
The defeat put a dent in the Giants' stretch run, dropping them four games back of the National League West-leading Los Angeles Dodgers and 2 1/2 games behind San Diego.
In the frantic Wild Card chase, San Francisco fell to three games behind the Padres and one back of the Philadelphia Phillies.
Still, it wasn't all gloomy for the Giants, as they didn't sag trailing 8-1.
The offense roared to life with a four-run outburst in the fifth, then Barry Bonds cracked homer No. 24 on the year and 732nd lifetime -- one shy of Hank Aaron's all-time NL homer mark -- and added a two-run double, while Moises Alou drove in three runs on a sacrifice fly and two-run double.
And following Bonds' big blast in the ninth to close the Rockies' margin to one run, Todd Greene ripped what looked like a game-winning blow to right field, only to see Brad Hawpe make a great catch near the wall.
"I thought I hit it good enough to get a hit," said Greene, who also had a walk, single and double in the contest. "For a right-hander to hit to the opposite field here is difficult, but I know I hit it good.
"It could have been a tie, but it doesn't matter -- we lost. We don't play this game on what-ifs."
Even manager Felipe Alou felt a jolt of electricity watching Greene's ball carry deep to right.
"I thought it would hit the fence and could bounce halfway to the field, but [Hawpe] made a good play," he said.
Hard to knock the hitters, though, who roughed up the Rockies with 13 hits overall, and Greene admitted the Giants believe they can win regardless of the score.
Hey, they trailed Colorado, 4-0, on Tuesday night and scored six runs in the second inning, eventually winning, 10-6.
"The last three weeks, we've been playing like a Major League team is supposed to play," said Greene. "We've been down before and come back. We hadn't had trouble throwing strikes, but the strike zone left us that one inning. They made us pay for it."
Lowry, who skipped a turn due to left elbow irritation, said he felt fine Wednesday and allowed only one run in the first four frames before tiring in the fateful fifth.
He would give up three walks and a hit before departing, then see the Rockies rampage for seven markers, three runs the responsibility of Jamey Wright.
"Just got my pitch count too high, and taking as much time off as I did, I think I ran out of gas," said Lowry. "My pitches started to get up and I wasn't able to make an adjustment."
The big hits for Colorado in the rally were two-run singles by Jeff Baker and Choo Freeman.
"I felt good for four innings, then the pitches started to get up in the zone," said Lowry, who threw 87 pitches over 4 2/3 frames. "I put myself and our team in a hole."
Like Greene, Lowry said he loved watching his club battle back.
"That's the mentality we're going to need down the stretch here," said the hurler. "Never-quit, never-give-up attitude. The guys did a great job battling back -- unfortunately for us, I put us in a hole and cost us the game."
Alou noted when he pulled Lowry, he said it was because of the high pitch count, but in the back of the manager's mind he was also worried about having Benitez and reliever Brian Wilson out with injuries and was forced to hold reliever Brad Hennessey in abeyance, just in case.
At least some help is on the way, with Triple-A Fresno right-hander Billy Sadler to join the bullpen Thursday.