CHICAGO -- Derrek Lee's offense is taking some of the pressure off the Chicago Cubs' depleted pitching staff.

Lee hit two homers for the second straight game and the fourth time this season to lead the Cubs to a 5-1 victory over the Colorado Rockies.

Before the game, Chicago placed right-handed ace Mark Prior on the disabled list.

Lee, the National League home run leader with 16, slugged a solo shot in the first and added a two-run homer in the Cubs' four-run sixth. He has 13 career multihomers games and has accomplished the feat on consecutive days twice.

"He's a big old man with big shoulders," Cubs manager Dusty Baker said. "If anyone can do it, it's him. He goes about his business quietly. He doesn't boast or brag or flaunt what he's doing."

It's nothing new for Lee, who has been carrying the Cubs through the first two months.

"I think I've had my swing pretty much the whole season," he said. "I don't think I've been this hot for so long."

And it's a good thing for the Cubs that he has.

Prior was placed on the disabled list after an MRI revealed a compression fracture just above his right elbow. He was struck by a line drive in Friday's win over the Rockies.

The Cubs also traded former closer LaTroy Hawkins and cash considerations to the San Francisco Giants on Saturday for right-handers Jerome Williams and David Aardsma. Chicago recalled right-hander Roberto Novoa from Triple-A Iowa to take Prior's spot on the roster.

Glendon Rusch (4-1) made his fifth strong start since rejoining the Cubs rotation, that is also missing Kerry Wood. Rusch allowed one run and four hits in seven innings and he hasn't given up more than two runs since becoming a starter again on May 7.

Michael Wuertz worked the eighth inning, and closer Ryan Dempster pitched the ninth in a non-save situation. For the eighth time in nine games, a Cubs starter pitched at least seven innings.

"It's a big boost for the ballclub when you get out and go deep in the game," Rusch said. "It takes a little pressure off the bullpen, espcially in this streak we have going with 20 games in 20 days.

"I feel good as far as being up there on my pitch count. I think I have more stamina lately, and in the last couple of starts, I've felt good late in the game."

Lee homered twice off Rockies starter Byung-Hyun Kim (0-4).

"He's hot man, he's hot," Colorado manager Clint Hurdle said of Lee. "There's no doubt about it. You don't want to give him a good pitch to hit."

Aramis Ramirez added a two-run shot off Kim in the sixth.

Preston Wilson had an RBI double in the fourth, and Dustan Mohr had two doubles for the Rockies.

Kim -- also a former closer -- made his second start of the season in place of Shawn Chacon who is out with a sprained right ankle. Kim allowed five runs and eight hits in five-plus innings.

"I think it was a situation where his location put him in some dire straights," Hurdle said. "He pitched very effectively through five innings."

Blaine Neal replaced Kim with none out in the sixth after Lee and Ramirez homered and pitched two scoreless innings.

Lee homered over the left-field bleachers in the first to give the Cubs a 1-0 lead, the first earned run Kim gave up to the Cubs in 11 appearances and 12 2/3 innings.

Colorado tied it in the fourth on doubles by Luis Gonzalez and Wilson.

The Rockies loaded the bases with one out in the fifth, but Rusch got Gonzalez to ground into an inning-ending double play.

The Cubs broke it open in the sixth on the two-run shots by Lee and Ramirez.

Notes

• Lee hit two homers in consecutive games on June 9 and 10, 2002 while with Florida.
• Rockies 1B Todd Helton went 0-for-4 and is 2-for-42 over the last 12 games.
• Colorado rookie SS Clint Barmes returned to the lineup after missing Friday's game with a sprained right ankle and was 0-for-3.