There has never been a team in history that had a seven-time Cy Young award-winner drop by in June to rescue its season. So only your friendly neighborhood psychics know what kind of impact Roger Clemens is going to have on the 2006 Astros.
But we should all remember one thing:
No history possibly can apply to this guy.
He's The Rocket.
The Astros are not paying this man nearly 3.7 million bucks a month to come back, sign some autographs and drive that train around their left-field railroad tracks.
And Roger Clemens knows it, too.
"I'm not here to ride around on the back of a convertible, selling tickets," Clemens said Wednesday. "They expect me to do it on the field."
So can he? Will he? Should he? And if he does that inimitable Roger Clemens thing of his, how will that change life in Houston, in the NL Central, in the National League wild-card free-for-all and on the rest of Planet Earth? Let's take a look:
The Age Factor
He's 43 years old. He's nine weeks from his 44th birthday. There are actual players running around the major leagues who didn't arrive in this world until after Clemens had arrived in the big leagues.
So ordinarily, you wouldn't find a team counting on a man this age to lead them anywhere -- except maybe to a Chamber of Commerce luncheon.
But have we mentioned Roger Clemens is no ordinary human?
Which allows us to look at this two ways.
If we were just going to look at ordinary humans, then history wouldn't be real encouraging.
Over the last 75 years, no non-knuckleballer Clemens' age (or older) has won 15 games in a season. And only two non-knuckleballers his age have had an ERA under 3.50 in a season of more than 100 innings pitched -- Nolan Ryan and Satchel Paige.
But those two guys were pretty much your classics freaks of nature. And if anyone qualifies as freak No. 3, it's Roger Clemens.
Over the last two seasons, pitching mostly at ages 41 and 42, no starting pitcher in the entire sport had a lower ERA than he did (2.43). Nobody.
Last year, pitching two-thirds of the season at age 42 and the final third at age 43, Clemens led the major leagues in ERA (1.87). It was the lowest ERA by any pitcher in his 40s since 1908 (when somebody named Cy Young hung up a 1.26).
So you tell us what history applies here -- the history this man keeps rewriting, or the kind of history that applies to the rest of the species? Want to bet against this guy? Go ahead. But we wouldn't.
The Health Factor
The Roger Clemens who headed for the mound in each of the last two Octobers was a physical mess. Sore calf. Sore quad. Sore hamstring. Sore back.
And nothing -- nothing -- tormented the Rocket Man more than that, more than finally getting his chance to pitch those games that matter most, and not being physically capable of pitching the way he can.
So it was fascinating to listen to him talk at his press conference Wednesday. He didn't talk about his age. He didn't talk about his stats. He didn't talk about his golf game. What clearly was on his mind, more than any other piece of this equation, was the health of his 43-year-old body.
"I can handle losing," he said. "I can handle pitching poorly. But I don't want my body to break down on me. If I [can't stay healthy], we're all wasting our time."
Well, no one knows yet if Clemens' body is going to break down on him between now and Halloween. Everybody in the history of mankind eventually got old -- even living legends. And where does that getting-old stuff show up? In those pulled hamstrings and strained calf muscles and floating bone chips. That's where.
So Clemens' agent, Randy Hendricks, told ESPN.com on Wednesday that Clemens is still so wary of stuff like that happening to him, he plans to use his three minor-league tuneup starts as sort of a final exam for his body. And if his body doesn't ace that exam, you might not see him take the ball June 22 at Minute Maid Park, no matter how much hoopla the Astros rolled out there Wednesday.
"I can handle losing. I can handle pitching poorly. But I don't want my body to break down on me. If I [can't stay healthy], we're all wasting our time."
-- Roger Clemens
"He's still testing himself," Hendricks said. "We have an agreement, but Roger is taking the position that he's got to be sure he's ready. These batters he's going to face are going to have 225 at-bats by the time he comes back, so he's got to be ready."
As 43-year-old people go, this is one 43-year-old who is in superhuman shape. But you never know.
The Hometown Factor
If there were no baseball franchise in Houston, Texas, you would not be reading this column right now. You wouldn't be reading it because Roger Clemens wouldn't still be playing baseball.
He wouldn't merely be retired. He'd be in his third year of retirement. He would have walked off the mound in Game 3 of the 2003 World Series and kept on walking.
That's because it wasn't the allure of playing baseball that lured him back. It was the allure of playing baseball in Houston.
The existence of the Astros, and the flexibility of the people who run the Astros, created a unique set of circumstances that made it possible for Clemens to keep pitching and still be the dad, husband, pro-am golf luminary, personal-appearance machine and larger-than-life local icon he aspired to be at this point in his life.
Now, three seasons later, that same set of once-in-a-baseball-lifetime circumstances is still pulsating, still drawing him back into a uniform. And in the end, it's the reason he's an Astro today, and not a member of the Yankees, Red Sox or Rangers.
He was flattered to be romanced by those three teams. He got spectacular offers from those three teams. He was clearly tempted by all of them, and especially by the thought of going back to Boston, to rewrite a final chapter that has stuck in his digestive tract for a decade and a half.
"But it always kept coming back," he said, "to, 'These are my guys here.' "
This time, though, besides all the hometown-hero perks he used to enjoy, he gets one extra perk that no one else could offer. He gets to go pitch a tune-up start next week for the Lexington Legends, and appear in the same box score as his son, Koby.
Just the thought of that chance inspired him to speak poetically Wednesday of the Griffeys and the Boones and the Bells -- the multi-generational families of modern baseball.
"That's pretty special when you see that," the Rocket said -- and it was a temptation he couldn't pass up.
But this is no one-sided arrangement he and the Astros have. They get a little something out of it, too. For the Astros, Roger Clemens is a certifiable franchise-changer.
They drew nearly 3,000 more paying customers last year when he pitched than they did when anybody else pitched. He almost singlehandedly -- with an assist from his pal, Andy Pettitte -- elevated his sport onto the Houston radar screen.
He is a man who possesses the unique charisma to draw these people out of the football-tinted universe they were once ensconced in -- and draw them into Minute Maid Park, for the sheer thrill of watching their very own legend make more history.
"These people are baseball fans now," one of Clemens' agents, Alan Hendricks, said last October. "They want to come to the park now. And they get into it, like they used to get into it at football games. It's like Yankee Stadium. You've been to Yankee Stadium when it's got a certain buzz to it, right? That's what this is like now."
Well, who's to say what that's worth -- to both of them? But apparently, it's somewhere in the neighborhood of $3.7 million a month.
The Short-Season Factor
There is always a method to Roger Clemens' madness. And this time around, it's a method that was calculated carefully by Clemens' agents nearly six months ago.
When it became clear early last December that the Astros weren't going to offer Clemens arbitration -- meaning he couldn't pitch for them again before May -- Hendricks began advancing the theory that maybe that wasn't all bad.
Maybe that eight-month grind, from mid-February through mid-October, was too long for a 43-year-old power pitcher. Maybe, if you looked at the way the Rocket's last two seasons ended, that was the moral of that story.
The months that get Rogers Clemens' blood pumping sure aren't April and May. They're September and October. And in each of the previous two seasons, when Clemens arrived in those months, he was like a marathoner who couldn't make it past Heartbreak Hill.
"Look, everyone knows [the Astros] weren't the best team that was interested in [signing Clemens]. But they can still win. And he thinks he can help them win."
-- Randy Hendricks, one of Clemens' agents
So in the end, he didn't just let down himself. He let down a team that dreamed of handing him the baseball with a whole season riding on it. And those unhappy endings inspired Hendricks to begin floating the plan that led everyone to the podium at Minute Maid Park on the final day of May:
The Roger Clemens Mini-Season Plan.
"What if," Hendricks said recently, "instead of getting to October and having a Roger who isn't himself, you had Roger at his best? Isn't that what everyone wants? And maybe the best way to do that is for Roger to pitch a three- or four-month season instead of a six-month season."
So that's the course that was plotted. And that's the course he and the Astros now will play.
Will this work? We don't know that yet. But we do know this:
Four and a half months into last season, Clemens had an ERA of 1.32.
And how many months are left in this season, if the Astros play all the way through October? Hmmm. That would be 4½ months.
That, friends, is no coincidence.
The Postseason Factor
Can Roger Clemens singlehandedly haul the Astros into the postseason, like a human tow truck?
But still, he changes everything.
This, after all, is a team that got off to a 19-9 start -- the same as the Mets. And the biggest reason this outfit has gone 8-18 since then is the crumbling of its pitching staff, which had the second-worst ERA in the league in May entering Wednesday (5.19).
But look beyond Brad Lidge's struggles and Pettitte's inconsistency and a disappointing bullpen. The biggest difference between the Astros of April and the Astros of May isn't any of that.
Their meltdown had a ripple effect on an overworked bullpen. Which had a ripple effect on an offense that has its own issues. Which made the return of Roger Clemens more vital to the future of this team than ever.
"He's coming back to Houston to help the Astros win," said Hendricks. "Look, everyone knows they weren't the best team that was interested in him. But they can still win. And he thinks he can help them win."
He's not coming back "because I need to," Clemens said, "or I want to. It's about winning."
They might not have the money now to add the big corner-outfield bat they need. But we have learned the last two seasons never to underestimate the power of the Rocket. So in the words of the man who signed the most unique contract of modern times Wednesday, "here we go again."
Jayson Stark is a senior writer for ESPN.com.