5 key factors that could decide the World Series

The Red Sox and Cardinals will open the World Series Wednesday night at Fenway Park in a rematch of the 2004 title tilt.

The two teams tied for the best records in baseball this year with 97 wins apiece, so on paper they appear about evenly matched. Being a Red Sox fan, I can say with confidence that Boston is the better team. Also, being a Boston fan, I must assume with confidence that the Cardinals will sweep the series.

Predictions aside though, here are five factors that could determine who comes away victorious.

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Cardinals pitching

While the Red Sox slugged their way to the World Series with baseball's most potent offense, the Cardinals will counter with one of the game's best pitching staffs. St. Louis pitchers had the fifth-best ERA in baseball this year, and they ranked second in FIP, a more nuanced metric of pitching performance that strips out the effects of fielding on run prevention.

They've been even better in the postseason behind the one-two punch of starters Adam Wainwright and Michael Wacha. Wainwright has a 1.57 ERA and 20 strikeouts in 23 innings of work; Wacha — who twice outdueled probable National League Cy Young winner Clayton Kershaw in the NLCS — has given up just a single run in 21 innings while striking out 22.

The one potential weak link in the Cardinals' pitching bulwark: Their relief corps. Cardinals relievers had only the 17th-best ERA this season. While that's better than the Tigers' 24th-ranked bullpen, it could spell trouble if Boston, as they did to Detroit, patiently wears down St. Louis' starters and then exploits its vulnerable pen.

Fastball hitters vs. fastball pitchers

The Cardinals threw fastballs at a higher rate (63.7 percent of all pitches) than any other team. And they were pretty good at it, too, posting the third-best fastball velocity in the game.

Boston's hitters feasted on fastballs during the regular season. Yet as Fangraphs' Eno Sarris pointed out, they had some trouble with the fastest of the bunch, swinging and missing way above league average on such offerings.

Against the Tigers' high-octane arms, Boston struck out 73 times in six games, while scratching together scant offense. If the same pattern holds for the World Series, the Cardinals could "reduce the Boston offense to one that looks a lot more league average," Sarris wrote.

"Everything gets tougher in October," he added. "Faster fastballs are just another part of that picture."

Boston's bullpen

The Red Sox assembled a lights-out bullpen down the stretch, topped with closer Koji Uehara. The ALCS MVP posted a ludicrous 0.51 ERA and 0.39 WHIP (walks plus hits per inning pitched) since being named Boston's closer in June. He's struck out 13 batters in nine innings of postseason relief, and played a role in every Red Sox win during the championship round, recording three saves and earning one win.

In the playoffs, Boston relievers have combined for a 0.84 ERA over 32 innings. And the team has a potent late-inning shutdown trio in Junichi Tazawa, Craig Breslow, and Uehara, who have given up just two runs over 21 playoff innings between them. If Boston can take a lead into the seventh inning, they are all but guaranteed to come away with a win.

The return of Allen Craig

The Cardinals have been without Craig since the first baseman went down with a foot injury in September. Craig isn't quite back to full strength yet, but he could still play a big role as the Cardinals' designated hitter in the games at Fenway.

Craig hit .315 during the regular season, and an amazing .454 with runners in scoring position. Though he'll be a liability on the bases with his nagging ailment, the value of his bat should more than make up for that. In the games played back in St. Louis, he'll be available as a late-inning pinch hitter, too, giving the Cardinals an extra weapon to bring off the bench.

Molina's arm

Yadier Molina is, almost without argument, the best fielding catcher in baseball. He's won five straight Gold Gloves, and he's thrown out an amazing 44.5 percent of would-be base stealers in his career, best among active catchers.

Boston, meanwhile, loves to run. The team ranked fourth in baseball with 123 steals in the regular season, and often used its speed to pick up extra bases on their opponents' miscues. In the playoffs, heads-up base-running helped the team come from behind to win the final game of the ALDS; two extra bases swiped via Tigers errors led to an epic walk-off win against Detroit.

Boston has already stolen 11 bases this postseason. They'll be more hesitant to run on Molina, though they won't give up the running game entirely.