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Picture this: It’s an October night and the Yankees are in one of those famous close-and-late situations, ones that unequivocally define a success or failure in a city where it’s more clear-cut than anywhere else. There are runners in scoring position and Francisco Cervelli is at the plate facing Rangers reliever Darren O’Day, he of the 4-2 record with a 1.95 ERA. Cervelli’s numbers in such circumstances aren’t too bad – .261 with RISP, .361 with RISP and two out and a whopping 6-for-10 with the bases loaded – but they’re masking agents for his current .215 second-half batting average and a projected .252-0-41.

O’Day deals his first pitch, one that to Cervelli looks delicious. Bat makes contact with baseball resulting in a routine ground ball to third base and a force out at second to end the threat – and perhaps the game and even the Yankees’ chances at repeating.

Cervelli’s a good guy and deserves props for making it to the Major Leagues direct from Double-A, but he’s not Jorge Posada. In the same situation against the Orioles Wednesday afternoon, one that had everyone screaming internally over why Joe Girardi did not send Posada up to pinch hit unaware of the facts, Cervelli failed. And if not for Nick Swisher’s heroics, the Yankees would have been victims of a three-game sweep to the last-place – yes they’re improving, but still – Baltimore Orioles on their home turf. Today’s off day would have been spent digesting the feeling one gets when a meal doesn’t agree with his or her insides.

But even with the victory came the biggest scare with Girardi’s announcement that Posada had “concussion-like symptoms.” Posada was evaluated, cleared to play and listed as day-to-day, but the Yankees’ postseason life was flashing before their eyes, along with a reminder of how the team is great and also fragile. Andy Pettitte, 38, has been out for two months with a groin strain. Derek Jeter, 36, may be healthy, but it doesn’t mean he’s not hurting; his 5-for-36 homestand and .262 batting average give the impression that the heavy mileage has, at least this season, taken its toll. Alex Rodriguez, 35, had hip surgery last year, and was hobbled and eventually disabled this year with a calf injury.

Don’t even think about the consequences of losing Mariano Rivera, 40, to any kind of injury – I don’t care how well the bullpen has performed since last July – but you were forced to consider the worst-case scenario of losing Posada for an extended time. A foul tip could break a bone in Posada’s pinky, and just like that Cervelli and Chad Moeller would be the Yankees’ postseason catchers since the team has no desire to throw 20-year-old Jesus Montero in any kind of pressure situation.

Posada was cleared, so he’ll travel to Texas, Tampa and Baltimore for the Yankees’ upcoming road trip, but the case studies of Jason Bay and Ryan Church, and for that matter anyone who’s dealt with concussion symptoms, prove that you cannot completely exhale.

"Whenever you're talking about concussions, there's concern," Girardi said prior to the test results being released. "If the tests come back OK, we'll probably take him with us. But if the tests don't, I'm not sure what you do."

Like some of the other older players, Posada’s numbers are modest (.262-17-53), and he’s been banged up with a Baker’s cyst behind his knee, a sore shoulder and calf, and a broken foot. But like Jeter, you can count on Posada in a money game and are confident that both will have a significant impact next month even if they limp to the regular season finish line.

“You're talking about a guy who's playoff-tested, World Series-tested, September-down-the-stretch tested, a switch hitter in the middle part of our lineup,” Girardi said. “It's an impact.''

Yankees fans, grab on with both hands and hold tight. Win or lose it’s going to be a jarring ride.

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