The progress report barely registered on the baseball world's seismograph, but to underestimate it means failing to understand the Yankees' current obsession. In an otherwise pointless September, the club is consumed with Mariano Rivera's steady recovery from a mysterious injury to his right shoulder.

The Yankees have very reason to sweat out the closer's rehab, considering he hasn't pitched since Aug. 15. He tossed without pain in a 35-pitch session in Tampa on Tuesday, and that two-word assessment -- no pain -- wasn't just good news; it was like an answered prayer to the entire front office.

	Mariano Rivera has been on the disabled list three times this season, twice with arm injuries.

The Yankees will now await the outcome of Rivera's next workout on Thursday, which the closer himself says is, "the biggest day."

Slowly but surely, the Yankees are allowing themselves to believe Rivera has finally conquered the muscle strain behind his right shoulder. In a best-case scenario, Rivera could return to the Bronx by Sept. 20, meaning the Yankees' bullpen might not be so naked in the postseason, after all.

"I'm expecting Mariano to be back. With the progress he's making, I'd be disappointed if he wasn't with us soon," said Yankees GM Brian Cashman.

With the Red Sox all-but-vanquished, the Yankees have slogged through September, entertaining themselves with mini-dramas in their starting rotation. Who stays, who goes, come the playoffs? Orlando Hernandez will almost certainly be exiled to long-relief, but manager Joe Torre is smart enough to say, "I'm not even close to deciding that."

A far more serous question is: who'll handle the ninth-inning leads against the A's or Twins, two potential postseason opponents who pose unique challenges to the Yankees. The A's have a superior starting rotation and the Twins have a better home record.

The Yankees have -- or had -- two distinct advantages over both clubs, as well as the Angels, should they win the wild card. The Bombers hit more home runs than anyone else and, thanks to Rivera, used to consider a save-conversion as one of life's guarantees.

But Rivera first started bleeding in Game 7 of the 2001 World Series against Arizona, when he failed to hold a one-run lead in the ninth inning. Then, only two weeks into the 2002 season, there was Shea Hillenbrand's stunning two-run home run in the ninth inning at Fenway Park, when the Red Sox rallied for a 7-6 win against Rivera.

	“	October is definitely a different time and having Mo come through for us is one of the most important reasons why we've been able to keep winning. Obviously, we're a much, much better team with him out there than not. But if he can't go, we're not going to give up. ”
		— Brian Cashman, Yankees GM, on Mariano Rivera

Little by little, the pebbles started trickling down the wall, and the Yankees closer finally lost some of his invincibility: he's been on the disabled list three times this year, twice for arm-related injuries, and the last time Rivera was shelved in August, teammates say his shoulder-pain was so severe he couldn't pick up his arm.

Most disturbing to the Yankees is that no one, not even Rivera, understood the cause of the injury, or how to prevent its recurrence. It certainly wasn't a result of poor mechanics; Rivera's delivery is as smooth and effortless as a golf-swing, and Torre has been careful not to overuse his closer in the last three years.

Maybe that's why Torre so grimly said he'd no longer count on Rivera's return in 2002, when the closer went back on the DL. "We'll wait as long as we have to," the manager said of Rivera's rehab. "And that includes into next spring."

So Rivera retreated to Tampa for two weeks of total rest -- a hiatus that included multiple visits to noted sports surgeon Dr. James Andrews. In the meantime, the Yankee bullpen did its best to cover the deficit. With Steve Karsay and Mike Stanton acting as the surrogate closers, the Bombers are a perfect 10-for-10 in save opportunities through Tuesday.

And the Yankees themselves flourished, going 16-9 since Rivera's last appearance, opening up a 9½-game lead on the all-but-expired Red Sox.

Still, no one in the Yankees family believes life will be this easy forever. After all, this is the softest month on the Bombers' schedule: after plaing a Labor Day weekend series against the Red Sox, the Yankees are playing all sub-.500 teams until Game 1 of the Division Series.

By then, the Yankees should have a firm idea if Rivera has healed, and whether his arm can withstand October's stress.

"October is definitely a different time and having Mo come through for us is one of the most important reasons why we've been able to keep winning," Cashman said. "Obviously, we're a much, much better team with him out there than not. But if he can't go, we're not going to give up."

Cashman insists the Yankees could, if necessary, survive with Karsay and Stanton -- even in a steel-cage match against the A's. But imagine the Twins without Eddie Guardado, who leads the AL with 40 saves. Or the A's without Billy Koch, right behind him with 39 saves.

Better yet, think of the Braves losing John Smoltz, who leads the majors with 49 saves, making a unique case for the NL's Most Valuable Player Award, let alone the Cy Young. It's true, the Braves exploited an otherwise weak NL East this year, but Smoltz has given them an invincibility that ... well, used to belong to the Yankees.

It might still. It all depends on how Rivera throws on Thursday and how, one workout at a time, he recovers from an injury no one truly understands. Fingers crossed, prayers uttered fast and furious, the Yankees and their closer cling to the two precious words that inspire hope for October:

No pain.

Bob Klapisch of The Record (Bergen County, N.J.) covers baseball for ESPN.com.