SAN FRANCISCO -- Reflecting their intent to vault back into contender's status immediately, the Giants signed free-agent left-hander Randy Johnson to a one-year, $8 million contract Friday.

Signing Johnson demonstrated the Giants' unwillingness to take any chances with their rotation, widely considered to be their biggest strength. Until signing Johnson, San Francisco wasn't assured of who would complement Tim Lincecum, Barry Zito, Matt Cain and Jonathan Sanchez. Left-hander Noah Lowry, the club's leading winner in 2005 and '07, underwent two forearm surgeries earlier this year and is not guaranteed to return in '09, although the team has said that his recovery is progressing smoothly.

Another starting candidate was right-hander Kevin Pucetas, who followed a strong regular season (10-2, 3.02 ERA at high Class A San Jose) with a solid effort for Scottsdale in the Arizona Fall League (4-1, 4.33, with a 3-to-1 strikeout-to-walk ratio). Pucetas, 24, owns a 32-7 mark with a 2.35 ERA in three Minor League seasons, but has not pitched above Class A.

By contrast, Johnson is one of the most accomplished pitchers in Major League history. The veteran of 21 big league seasons has won five Cy Young Awards and made 10 All-Star teams while compiling a 295-160 career mark with a 3.26 ERA, 100 complete games and 37 shutouts in 596 appearances. Known to be highly motivated about the chance to secure his 300th career victory -- he'd be the 24th pitcher to achieve that milestone -- Johnson ranks second all-time with 4,789 strikeouts.

Even at age 45, Johnson remained effective last season, posting an 11-10 record with a 3.91 ERA in 30 starts for the D-backs. He ranked third among National League pitchers with a 3.93 strikeout-to-walk ratio and sixth with 8.46 strikeouts per nine innings. His 2.41 ERA following the All-Star break ranked fifth among NL hurlers.

Johnson becomes the third Cy Young Award winner on the Giants' staff, joining the NL's reigning winner, Lincecum, and Zito, the 2002 AL Cy Young Award recipient. The last team with three Cy Young winners on the same roster was the 2002 Braves, who boasted Tom Glavine, Greg Maddux and John Smoltz.

Johnson's arrival will prevent the Giants from placing undue pressure on Lowry to heal and enable them to develop Pucetas and two of their other top pitching prospects, 2007 first-round Draft picks Madison Bumgarner and Tim Alderson, at a leisurely pace.

"It's a good bridge," Giants president Larry Baer said. "A lot of our promising young pitchers are a period of time away. [Johnson] can have a major impact next year."

With Johnson aboard, speculation is likely to increase that the Giants will trade a pitcher for a much needed, offensively proven corner infielder who can bolster the middle of the batting order -- San Francisco's remaining void. However, general manager Brian Sabean has steadfastly refused to part with any of the Giants' top pitchers, from mainstays of the rotation to top Minor Leaguers. For example, he resisted entreaties before and during the Winter Meetings to swap Sanchez.

As a local product -- he's a native of Walnut Creek, Calif., and graduated from Livermore High School in 1982 -- Johnson was interested in San Francisco from the outset of free agency. And the feeling was mutual. It helped that the Giants are NL West rivals with the D-backs and train in Scottsdale, a short drive from Johnson's home.

"We've been talking to them on and off for a few days, and in the last three or four days, Brian and I had a lot of conversations," said Johnson's agent, Barry Meister. "It kind of fit the bill. Randy wanted to stay in the West, train in Arizona, play at home and against the Diamondbacks. We thought it was a good idea."

Johnson's contract includes $2.5 million in performance bonuses and $2.5 million in awards bonuses, according to an industry source.

The Giants have signed four free agents, more than any other NL West team. They obtained relievers Jeremy Affeldt and Bob Howry and shortstop Edgar Renteria earlier this offseason.