There is one overriding factor that equates with season-long success in baseball, one attribute that turns good teams into champions and great teams into juggernauts. That factor is rotation health — keeping your best starting pitchers on the mound as frequently and consistently as possible.

The Red Sox’s Daisuke Matsuzaka was lost for the season in May because of a blown-out elbow. (GREG M COOPER/REUTERS)

Moving ahead to 2011, there are several reasons why the Philadelphia Phillies are the best team in baseball, but chief among them is the fact their top three starters (Roy Halladay, Cliff Lee and Cole Hamels) have made every start this season, while their fourth-best, Roy Oswalt, is back at the top of his game following a six-week absence because of a back injury. The Phillies have used just seven starting pitchers all season. Similarly, the Detroit Tigers, the best team in the AL at the moment, will soon have four starters with 30 starts apiece, and a fifth, newly acquired Doug Fister, who has 30 this season between Seattle and Detroit.

The big story in baseball this week is the twin collapses of the wild-card leaders: the Boston Red Sox in the American League, and the Atlanta Braves in the NL. Both had huge leads at the beginning of the month but are hanging on by an elbow ligament in the face of hard-charging challenges. The Red Sox lead the Tampa Bay Rays by just two games, while the Braves’ lead is down to 2 ½ over St. Louis and 3 ½ over San Francisco.

The Red Sox and Braves each have their own unique set of problems, but they share the biggest one: a devastating rash of injuries to their starting rotations.

For the Red Sox, Daisuke Matsuzaka was lost for the season in May because of a blown-out elbow, and Clay Buchholz hasn’t pitched since a back injury sidelined him in mid-June. Josh Beckett and Erik Bedard have each dealt with nagging injuries that caused them to miss starts this month. The Red Sox have utilized 10 starting pitchers this season. Most big-payroll teams can go six or seven deep with serviceable big-league-quality starters. Few can go 10 deep.

Meantime, the Braves have been without Jair Jurrjens and Tommy Hanson, two of their top three starters, since August. Amazingly, they have entrusted 53 percent of their September innings (91 out of 1702 / 3 total) to rookies — the kind of thing of a rebuilding team might do down the stretch, but something that is practically unheard of for a championship hopeful such as the Braves.

In has become fashionable — especially in the case of the Red Sox, whose vast resources make it easier to cover up mistakes -- to assign blame to the front office for failing to put together enough depth to withstand some injuries. It is a valid claim. Veteran John Lackey, who has a major-league-worst 6.49 ERA in the second year of a five-year $82.5 million deal, appears to be a monumental mistake on the part of GM Theo Epstein. The Red Sox’s farm system was of little help, offering only fringy prospects such as Andrew Miller and Kyle Weiland as fill-ins. And Bedard, a trade-deadline pick-up, carried a high degree of risk given his lengthy injury history.

But there are also some years when pitching injuries simply torpedo your season, and there isn’t anything that can be done about it. The one New York Yankees team that missed the playoffs in the past 16 years — the 2008 version — suffered through one of those seasons. Only Andy Pettitte and Mike Mussina remained healthy. The rest of the season was a horror show, with a steady parade of Darrell Rasners and Sidney Ponsons and Dan Gieses taking the mound.

The 2011 Red Sox and Braves might still hold on to their wild-card leads. They might even go on a nice run in the playoffs (it would help in that pursuit to have Buchholz, Jurrjens and Hanson back). But if they fall short, it will have had less to do with choking or front-office negligence than with the simple reality of baseball: Nothing can doom a season faster or more acutely than injuries in the starting rotation.