The NL East leaders lost another game and two more players.
Blanton was scratched minutes before the game because of inflammation in his elbow, and Victorino hasn't started the last four games because of a right hamstring strain.
"We're losing people every day and it's got to stop sometime," manager Charlie Manuel said. "We've got guys playing who when the season started were on the bench, and a couple were Triple-A guys."
Five-time All-Star second baseman Chase Utley and former closer Brad Lidge have been sidelined all season. Outfield prospect Domonic Brown is in Triple-A after getting hurt in spring training, and reliever Jose Contreras and backup catcher Brian Schneider are on the DL now. Roy Oswalt, catcher Carlos Ruiz, reliever J.C. Romero and Blanton spent time on the DL earlier this season.
Jhoulys Chacin was the beneficiary of Giambi's turn-back-the-clock power display. Chacin (5-2) allowed one run and four hits, striking out a season-high nine in seven innings.
Making a rare start at first base in place of Todd Helton, Giambi went deep in his first three at-bats. The 40-year-old former AL MVP entered 3 for 26 (.115) this season with one home run and four RBIs.
With two chances to match the major league record of four homers in a game, Giambi struck out looking against Scott Mathieson in the sixth and went down swinging against Romero in the ninth.
"I was up there letting it fly, giving it some whacks," Giambi said.
Giambi hit a three-run drive into the second deck in right field in the first inning off Kyle Kendrick (3-3). He lined a two-run shot to right off Kendrick in the third. Giambi hit another two-run shot to right off Danys Baez in the fifth.
It was the third time in eight days that a big league player hit three homers in a game. Carlos Beltran did it for the New York Mets last Thursday and Toronto slugger Jose Bautista accomplished the feat Sunday.
Giambi is the 12th Rockies player to homer three times in a game. Larry Walker was the last to do it on June 25, 2004, at Cleveland. Giambi has 419 career homers and 39 multihomer games.
Kendrick allowed five runs and seven hits in three innings.
"I felt great but it was a rough night," he said.
When Giambi connected in the first to give the Rockies a 3-0 lead, the game was pretty much over. The Phillies have slumped terribly on offense. They have 10 runs and 28 hits in their last six games, going 1-5.
"We've got to hit better," Manuel said. "We don't have balance in our lineup. We've got to stay at it and get going."
Giambi struck out against closer Ryan Madson with the tying run on second base to end Wednesday night's 2-1 loss. But he looked like the old Giambino in this one.
Giambi was the 2000 AL MVP with Oakland when he hit .333 with 43 homers and 137 RBIs. He hit 41 homers twice with the New York Yankees, and had 32 in his last season as a full-time starter in 2008. He's been a role player the last 2½ years.
During the Barry Bonds trial this year, Giambi publicly admitted that he previously used steroids.
On a night when it rained steadily early in the game, the highlight for Phillies fans came when pitcher Cliff Lee batted for Kendrick in the third. Lee got a loud ovation from the fans who remained in their seats. He was even cheered as walked back to the dugout after striking out.
Lee, off to a subpar 2-4 start, is the fan favorite on a team filled with players who've accomplished more in Philadelphia.
The Phillies got their only run when Raul Ibanez hit a ground-rule double in the fourth.
NOTES: A crowd of 45,425 was the 158th straight sellout at Citizens Bank Park, including postseason play. ... The Phillies have gone down 1-2-3 in 13 of their last 29 innings. They've scored more than three runs just six times in May and are 8-9 this month. ... Philadelphia slugger Ryan Howard is hitless in his last 20 at-bats.