The story will be a sweet one — if the plot cooperates.

Randy Johnson is indeed coming home. He grew up in Livermore, Calif. Played in the Granada Little League. Pitched on the diamonds at Baer Park, out behind Mendenhall School. From there, it's just a 45-minute drive to the gates of AT&T Park. That would be one minute for each of Johnson's birthdays.

"It's exciting to come back," Johnson said Saturday in his first remarks after signing a one-year, $8 million contract with the Giants.

In the team's vision, the plot will go this way in 2009: Johnson takes the final lap of his guaranteed Hall of Fame career in style. He classes up the rotation even further. He finishes with 12 to 15 victories, wins his 300th game in a Giants' uniform and helps mentor young players. And the Giants contend in a weak National League West.

"He's here for one reason," General Manager Brian Sabean said of Johnson. "And that's to help us make a run at this division." Forgive him, for he knows that season-ticket renewals are in the mail.

In baseball, December is the optimist's month. But please, let's not pile too much sugar on the compost pile.

The Giants are not World Series contenders. They weren't before they signed Johnson, and they aren't now that they have. The rotation is deep. But the batting order remains more shallow than Britney Spears' reading list.

That said, signing Johnson is a very smart move by Sabean. It is fairly low risk - just a one-year commitment - for a potentially high return.

This is definitely no publicity stunt. It isn't like the 1986 move in which the Giants picked up Steve Carlton in his dotage to pitch just 30 innings (and allow 20 runs) before sending him along on a few more undistinguished stops on the way to Cooperstown.

Johnson still has plenty of game in his left arm, if not as much velocity. The deep outfield recesses of AT&T Park should suit his reinvention as a flyball pitcher. He has spent the past couple years rallying from back surgery, and grew stronger as his 2008 season in Arizona progressed. He had a 2.41 ERA after the All-Star break, and in his final start pitched a complete game in a 2-1 win.

On his conference call with Bay Area media, Johnson sounded very much all-business. He was eager to speak of how far along he is in his off-season conditioning. There's no question the team will get Johnson's maximum output, whatever it is.

But if Sabean truly wants the team to sniff a playoff spot, this can't be the last deal he makes. He is far more of a realist than his remarks often make him sound. Just read between the lines - and the maneuvers.

The blunt truth: Sabean signed free-agent infielder Edgar Renteria because the Giants' farm system has not produced enough top-tier position players over the past 10 years. And Sabean signed Johnson because he could not find any affordable position players with middle-of-the-lineup pop.

"If we couldn't satisfy what we needed to do offensively," Sabean said, "then let's get better, if possible, on the defensive end." Johnson was just as pragmatic when talking about the Giants' playoff potential, grading on the curve. There are no fearsome rosters in Los Angeles, San Diego or Arizona.

"I think the N.L. West has not been labeled one of the top strongest divisions," Johnson noted, throwing the verbal equivalent of his backup slider.

At the very least, the Giants just became more interesting than they were three days ago. What's so bad about that? It is difficult to imagine a heartwarming saga being built around Johnson's stern visage.

But if he can punctuate his career with an exclamation point, near his spawning grounds, he might become sentimental in spite of himself.

The story will be a sweet one — if the plot cooperates. In December, we are allowed to believe it might.