The Associated Press

MESA, Ariz. - Mark Prior will start the season on the 15-day disabled list because of inflammation in his right Achilles' tendon.

The Chicago Cubs star has been throwing off the mound in spring training, but has not pitched in a Cactus League game because of the injury.

He was originally scheduled to start the team's third game of the season on April 8 at Cincinnati's Great American Ball Park.

If Prior doesn't pitch in any major league exhibition games, he would be eligible to come off the disabled list on April 10.

The Cubs hope to have him for their first homestand April 12-19.

"We're happy with the way he's coming along," general manager Jim Hendry said Tuesday.

"He's progressing the way we had hoped. We're going to always be cautious."

Prior, 23, was 18-6 with a 2.43 ERA and 245 strikeouts in his first full big league season last year, finishing third in voting for the NL Cy Young Award.

The hard-throwing right-hander first felt soreness in his Achilles' last September as he helped pitch Chicago to the NL Central title, going 10-1 over the final two months of the season.

Barry Bonds hit a three-run homer in the first inning Tuesday, but the Cubs still breezed past the San Francisco Giants 12-4.

Sammy Sosa went 2-for-3, Derrek Lee was 2-for-2 and Alex Gonzalez was 2-for-3 as the Cubs outhit the Giants 18-5.

Carlos Zambrano was solid after the first inning, improving to 3-0 this spring.

He worked six innings, giving up three runs and three hits.

He didn't walk a batter and struck out two.

Giants starter Kirk Rueter allowed six runs and eight hits in three innings.