Would the Arizona D-backs have won the 2001 World Series without Danny Bautista? How about the Angels the next year without Francisco Rodriguez? What about the Giants last year without Marco Scutaro?

And an even better question than all of those: Did anyone in their right mind think those three would be among the most important players in their club's march to a championship?

It seems that as long as there's been baseball in October, there has been a key ingredient to a title team that comes from an unexpected place: an X-factor who somehow decides to play the best baseball of his life in the chilly air in front of packed crowds with the biggest stakes in the game on the line.

So who's it gonna be this year? The MLB.com beat reporters of each pennant contender gave their top X-factor choice for October 2013:

Boston Red Sox: He can play a little first base and he can play a little outfield. But the main reason Mike Carp has a chance to make waves for the Red Sox in the playoffs is because he can hit. Entering Thursday, Carp had a .295/.363/.524 slash line this year, with nine home runs and 42 RBIs.

Detroit Tigers: The Tigers like Don Kelly. He has a bit of pop -- six homers in 208 at-bats this year -- and can come up with a clutch hit from time to time. He's hitting only .231 this year entering Thursday's action but is batting .286 with a homer in 13 career postseason games.

Oakland A's: Through Wednesday, catcher Stephen Vogt has four homers and 16 RBIs in 129 at-bats, and the A's like the way he's been swinging the bat so much that it's possible they'll carry three catchers -- Kurt Suzuki, Derek Norris and Vogt -- on their 25-man playoff roster.

Tampa Bay Rays: What a comeback for Alex Cobb after taking a line drive off the head on June 15. Since his return two months later, the young right-hander has evolved into Tampa Bay's best starter down the stretch, using an excellent curveball to become a dominant strikeout pitcher in his last two wins. Entering Thursday's start, Cobb had pitched eight innings or more in three of his last five outings. That's a postseason-type horse any team would want in October.

Cleveland Indians: It's admittedly weird seeing the name Jason Giambi in this group, but the guy is 42 years old and is batting .185 this year. Then again, he can still hit homers -- he had nine in 184 at-bats through Wednesday -- and he often hits them at the right times, such as his game-winning two-run pinch-hit job against the White Sox on Tuesday.

Texas Rangers: He's a veteran outfielder who has never tasted the postseason, but there's a good indication that Alex Rios could be ready for it. He's been a steady bat and clubhouse presence with the Rangers since arriving via trade on Aug. 9, and he still has power, with six homers in 168 at-bats with Texas entering Thursday.

Atlanta Braves: Since arriving from Kansas City and starting games at second base ahead of struggling Dan Uggla, Elliot Johnson has found ways to contribute. Johnson won't hit for power, but he has been excellent in the field and can steal bases. These are key elements of winning postseason baseball.

St. Louis Cardinals: Anyone who hits 17 homers in 284 at-bats is a threat to do serious damage in the playoffs or in any game. And anyone who has watched any Cardinals games this year knows how valuable bench bat Matt Adams has been. He has a flair for the dramatic and he has won the hearts of the Busch Stadium fans. We'll see if he's ready for the biggest stage.

Los Angeles Dodgers: He got huge hits for the World Series champion Chicago White Sox in 2005 and he got huge hits for the World Series champion San Francisco Giants in 2010. Now Juan Uribe is 34 years old and waiting for another chance to do something big in the playoffs. Don't bet against him.

Pittsburgh Pirates: He was once a touted prospect for a struggling team, but now Jose Tabata is a key bench asset for a powerhouse. Since taking over for Starling Marte in the leadoff spot after Marte suffered a hand injury on Aug. 18, Tabata has 10 extra-base hits and 15 RBIs entering Thursday. Marte is back, but Tabata won't be far away for manager Clint Hurdle to call on again.

Cincinnati Reds: What more needs to be said about Billy Hamilton? He's always a huge threat to steal bases -- more than one per trip around the diamond, in fact. His mere presence on the basepaths as a pinch-runner can alter games. Manager Dusty Baker can't wait to get him on first in a key situation and see what he can do.