Johnson, unable to reach a contract agreement with the Diamondbacks, opted for free agency on Thursday, the final day players could file.

"Randy instructed us not to file for free agency until we made every effort to reach an agreement," Johnson's agents, Barry Meister and Alan Nero, said in a statement. "The Diamondbacks have a budget based on their club's financial situation and obviously viewed Randy's contract in that context. Randy considered every reasonable compromise including offering to take a 50 percent pay cut, all to remain a Diamondback. However, the economic situation did not lend itself to an agreement."

Johnson's two-year contract with the Diamondbacks averaged $13 million per season. His actual salary last season was $10 million.

The Diamondbacks' offer, then, did not exceed $5 million. It was believed to be in the $2 million to $3 million range.

Arizona general manager Josh Byrnes, who said the sides had conversations through the week into Thursday, would not rule out still signing Johnson but added "something would fundamentally have to change in our position or their position or both."

Five victories short of 300, Johnson intends to pitch next season, but almost certainly will sign with another team.

"Randy can be a difference-maker," Meister said. "I expect there to be significant interest."

Johnson, who went 11-10 with a 3.91 ERA while pitching 184 innings last season, has not earned less than $9.1 million since 1998.

The Diamondbacks balked at paying $10 million or more to a 45-year-old pitcher with a history of back trouble — even though Johnson's countdown to 300 victories likely would boost attendance.

Just last Friday, the Diamondbacks dismissed 31 front-office employees, citing rising costs and the troubled economy. The team says it maintains one of the largest full-time workforces in baseball, but its budget is an obvious concern.

As a free agent, Johnson almost certainly would be attractive to certain teams on a one-year deal. The market is relatively thin in starting pitchers, and Johnson would be aiming for a milestone — and more.

Byrnes praised the spirit of the conversations with Johnson's camp.

"Both sides worked very hard to find an equitable deal," Byrnes said. "We couldn't do it."

Byrnes said the club envisions a rotation of Brandon Webb, Dan Haren, Doug Davis, Max Scherzer and Yusmeiro Petit next season.

"There's a chance we might try to find another person that would add to our depth," Byrnes said.

Johnson is a five-time Cy Young Award winner. He won the NL Cy Young from 1999-2002 with Arizona.

The Big Unit was co-MVP with Curt Schilling in the 2001 World Series victory over the New York Yankees. He went 21-6 with a 2.49 ERA and 372 strikeouts that year.

Johnson has 4,789 strikeouts, second to Nolan Ryan on the career list, and pitched a perfect game.

Johnson came back for a second stint with the Diamondbacks in 2007 after a trade with the Yankees. He underwent the third back surgery of his career that year.

In January 2005, the Diamondbacks traded him to the Yankees. Johnson and his family have long made their home in the Phoenix suburb of Paradise Valley.

"Randy will miss the overwhelming support the fans have shown him throughout the years," his agents said. "He wishes the Diamondbacks great success in 2009 and beyond."

The Associated Press contributed to this report.

Arizona Diamondbacks News News » With 300th win near, Johnson files for free agency 2008-11-14
With 300th win near, Johnson files for free agency 2008-11-14
First, Trevor Hoffman. Now, Randy Johnson. Future Hall of Fame pitchers are bolting their teams at an alarming rate this offseason. MLB Hot Stove