SAN DIEGO -- The Padres didn't set out this offseason to add to their starting rotation, but with James Shields still available less than two weeks before pitchers and catchers report for Spring Training, they decided they couldn't pass on the durable right-hander, agreeing to a four-year deal late Sunday.

The Padres announced the signing and introduced Shields on Wednesday.

Shields' deal, which was pending a physical, includes a club option for a fifth season and is worth between $72 million and $75 million, according to a source. CBSSports.com reported that it is worth $75 million, which includes a buyout of the fifth year.

Shields is the first free-agent pitcher to sign a contract in excess of $50 million after Feb. 1 of a given year. His is also the largest deal the Padres have made with a player, surpassing the three-year, $52 million deal Jake Peavy signed in 2007 after he won the National League Cy Young Award.

Shields, 33, gives the Padres a formidable starting rotation to match their revamped offense, one that first-year general manager A.J. Preller spent much of his time on this offseason, acquiring outfielders Justin Upton, Wil Myers and Matt Kemp, among others.

In Shields, the Padres added a workhorse for the top of the rotation, giving them four strong starters as he will join Andrew Cashner, Tyson Ross and Ian Kennedy to give the team one of the top rotations in the NL.

Shields, a nine-year veteran who won 14 games and had a 3.21 ERA for the American League-champion Royals last season, has made 33 or more starts in each of the past seven seasons. Consider that since 2011, Shields ranks first among starting pitchers in innings, 15th in ERA, 19th in strikeouts-to-walks and 19th in opponents' batting average.

Shields moved to Rancho Santa Fe, Calif., approximately 25 miles north of downtown San Diego, about a year ago, and that might have factored into his decision to join the Padres. That he didn't have a baseball home so soon before Spring Training might have as well.

In the end, it wasn't clear who the Padres were competing against for Shields, who reportedly had an offer of five years and $110 million earlier in the offseason. But as the calendar flipped to February, teams had their rotations -- and their payrolls -- mostly set for the start of the season.

Enter the Padres, who kept tabs on Shields even while they were addressing their primary need -- offense.

San Diego executive chairman Ron Fowler told MLB.com last week that he had given Preller "financial flexibility" to make additions and increase payroll, which was less than $90 million before the Shields deal. That figure has now pushed closer to $105 million, which will be a franchise record.

"I believe A.J. feels he has sufficient flexibility to make a deal if it is the right fit," Fowler said in an email. "I very much respect his discipline in looking at options."

Myers, who was the centerpiece of the trade from the Royals to the Rays in December 2012 in which Shields went Kansas City, said he heard nothing but good things from his many of his former teammates from both teams about Shields.

"They would be getting a workhorse, an established big league pitcher," Myers said of Shields on Saturday. "He has been a leader on both teams he's been on. ... I would be excited to get him. He's a great pitcher."

While pitching certainly wasn't at the forefront of the Padres' offseason wish list, the team has been receptive to adding arms.

Preller added two power right-handers to the back end of the bullpen in trades, getting Brandon Maurer from the Mariners and Shawn Kelley from the Yankees. Earlier, he signed free agent Brandon Morrow to a one-year deal for $2.5 million. Morrow is expected to compete for a spot at the back end of the rotation.

But there were some in the organization who were hopeful the team would add another starting pitcher, not only to give the team additional depth but quality depth. Shields gives them that and much more.

Cashner, who has thrown some of the most electric and dominant games in franchise history, has been on the disabled list three times in the past three seasons. Ross, an All-Star a year ago, has thrown more than 125 innings just once in his career. Kennedy can be a free agent after this season.

The signing of Shields would essentially mean that there will only be one open spot in the rotation this spring, a competition that figures to be between Morrow, Robbie Erlin and Odrisamer Despaigne.

Because Shields' former team, the Royals, made him a qualifying offer after the season, the Padres have to surrender their first-round Draft pick (13th overall), but the blow could be lessened if they regain a compensatory Draft pick next year if they make a similar qualifying offer to Upton, a potential free agent after this season, and he turns it down and signs with another team.

There are some who contend that Shields, as durable as he's been in his career, has a lot of miles on his right arm and that he's a candidate for regression.

After all, according to FanGraphs, no one threw more pitches (4,080) than he did last season -- of course, the Royals reaching the World Series had plenty to do with that. Some might nitpick Shields' postseason performance as well -- a 5.46 ERA in 59 1/3 career innings. He lost twice to the Giants in the World Series last fall.

But his velocity has shown no depreciation. In fact, it's gotten better. FanGraphs had his average fastball velocity in 2014 at 92.5 mph, up from 90.9 in 2011. There's a history of durability that managers crave, too.

San Diego manager Bud Black, like Shields a former Royal, talks often about pitchers who "go to the post" and the value of a starting pitcher who can throw 200-plus innings.

Shields has topped 200 or more innings in each of the past eight seasons.

"Two hundred innings is a high standard in today's era," Black said last season. "The strength of any club is in the innings and the starting rotation. If you have your best five guys go to the post and pitch close to 1,000 innings, you're probably going to the playoffs."