PHOENIX -- Brad Penny added six effective innings to the best spring of his career on Thursday, and manager Joe Torre then added to Penny's resume by naming him the Dodgers' Opening Day starting pitcher.

"Why not?" said Torre. "He was pretty good. Barring anything in his last start, we've sort of planned it that way and no reason not to do that."

Penny is likely to be followed by Derek Lowe, Chad Billingsley and Hiroki Kuroda. The Dodgers won't need a fifth starter until April 8, with Esteban Loaiza and Chan Ho Park the finalists. Lowe started the three previous Opening Days for Los Angeles.

The Dodgers open at home Monday, March 31, against the Giants. It will be the first Opening Day assignment for Penny, who is coming off back-to-back 16-win seasons and was the National League starting pitcher in the 2006 All-Star Game.

"I've never done it and I'm sure I'll be excited," said Penny, who allowed one unearned run in the Dodgers' 8-2 win over the White Sox. "I'll go out like a regular start, just get outs. You don't get too emotional for a start like that. I don't compare it to the World Series or a playoff."

A hero of Florida's 2003 World Series championship against Torre's Yankees, Penny has been lights-out all Spring Training, in contrast to a year ago, when he had an 8.44 spring ERA. He's allowed one earned run in 16 innings (0.56 ERA), which doesn't count five scoreless innings in a Minor League game.

"I can't explain it. I usually don't have good springs," said the 29-year-old. "Last spring was horrible. I didn't have a split or curveball. There's no rhyme or reason."

Torre praised Penny's command and splitter while facing the entire White Sox anticipated starting lineup, while Penny said his gradual improvement to staff ace has as much to do with what's above his arm.

"I'm mixing up my pitches better and getting smarter," he said. "I'm in and out, up and down. When I locate the four-seamer, the hitters don't know what's coming when I get behind. In the past, they knew they were getting a fastball. Now, they're not so sure."