Mark Prior, Jason Schmidt and Larry Walker are struggling to recover from injuries.

Mariano Rivera is healthy and committed to the New York Yankees for at least two more years.

Prior will start the season on the 15-day disabled list because of inflammation in his right Achilles’ tendon. The Chicago Cubs pitcher has been throwing off the mound in spring training, but has not pitched in a Cactus League game.

He originally was scheduled to start the team’s third game of the season April 8 at Cincinnati. 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 in Mesa, Ariz. “He’s progressing the way we had hoped. We’re going to always be cautious.”

Rivera and the Yankees agreed to a $21 million, two-year contract extension that runs through 2006. New York owner George Steinbrenner watched as the deal was announced in Tampa, Fla., and gave the reliever a hug.

“I think I was born to be a Yankee,” said Rivera, one of the best closers in baseball history. “I want to thank Mr. George to get the opportunity to stay with the Yankees forever, have a chance to get into the Hall of Fame with the pinstripes. That’s big for me.”

Schmidt will miss his second straight spring start Thursday because of a sore shoulder, raising doubt whether he will be ready for San Francisco’s season opener at Houston.

“He’s borderline right now only because there’s not enough time,” pitching coach Dave Righetti said in Scottsdale, Ariz.

Doubtful, too, is closer Robb Nen, whose workload was cut back because of discomfort in his right shoulder. He’s had three shoulder operations in the last 16 months and missed the entire 2003 season.

“We want to reassess everything and make sure we’re not going too fast,” trainer Stan Conte said. “In light of everything that’s happened to him, we decided to pull back. He’s made up so much ground this spring.”

Tests determined that Nen’s soreness was unrelated to the operations, Conte said.

Walker’s strained left groin has not improved, putting his availability for opening day in jeopardy. The Colorado Rockies slugger and 1997 NL MVP has been sidelined most of the spring because of the injury.

In spring training games:

Yankees 3, Reds 2

At Sarasota, Fla., Jose Contreras showed he’s ready for New York’s season-opening trip to Japan, pitching five hitless innings before losing his touch.

Mets 9, Expos (ss) 5

At Viera, Fla., Mike Piazza homered twice and drove in five runs. He’s hitting .387 with four homers and 16 RBIs this spring.

Astros 12, Braves 3

At Kissimmee, Fla., Roger Clemens struck out six in five scoreless innings.

Marlins 11, Dodgers 1

At Jupiter, Fla., Alex Gonzalez went 4-for-4 to raise his exhibition batting average from .161 to .257. Jeff Weaver allowed seven runs — five earned — and 10 hits in three innings.

Red Sox 7, Devil Rays 4

At Fort Myers, Fla., Derek Lowe needed only 70 pitches in six shutout innings. In 181/3 innings over four starts this spring, he has allowed two earned runs for a 0.98 ERA and just three walks.

Blue Jays 10, Indians 9

At Dunedin, Fla., Frank Catalanotto hit a grand slam off Jason Bere, who further jeopardized his chance to make Cleveland’s starting rotation.

Pirates 8, Phillies 2

At Bradenton, Fla., Billy Wagner struck out one, walked one and allowed a hit in a scoreless inning.

Expos (ss) 3, Orioles 0

At Fort Lauderdale, Fla., Sun-Woo Kim pitched five innings of two-hit ball, and Seung Song allowed three hits in three innings. Randy Choate worked the ninth for his second save.

Angels 7, Brewers 2

At Tempe, Ariz., Aaron Sele turned in his best outing of the spring, limiting Milwaukee to four hits over five scoreless innings.

Cubs 12, Giants 4

At Mesa, Ariz., Barry Bonds hit a three-run homer. Carlos Zambrano worked six innings, improving to 3-0 this spring. Giants starter Kirk Rueter allowed six runs and eight hits in three innings.

White Sox 13, D’backs 5

At Tucson, Ariz., Scott Schoeneweis pitched five innings for Chicago, allowing four runs and eight hits.