The Post Sports Live crew debates which single player is most important to the Nationals’ overall success in 2014. (Post Sports Live/The Washington Post)

As star pitchers go through their first few spring training games, we watch as if a bomb squad is defusing a booby trap. We witness exhibition games with our hands over our eyes, peeking through our fingers. Whose elbow or shoulder will detonate next?

March is baseball’s most morbid month as pitchers, who inflict small injuries on themselves every time they engage in the unnatural act of big league pitching, try to ramp up from a winter of total inactivity (to heal) to maximum effort before April Fool’s Day.

A pitcher’s arm can blow — or simply strain, squawk and send its owner to the disabled list — on any pitch any day of the season. But this month seems the most dangerous, as baseball offers an entirely different meaning for March madness.

The most upsetting image from spring training so far was the Braves’ Kris Medlen walking off the mound Sunday in mid-inning, holding his elbow, heading past trainers and manager, directly into the darkness of the Atlanta locker room tunnel.

His expression — season over? career in jeopardy? — has become a regular, though utterly unpredictable, part of baseball. The National League East alone knows what it feels like when the bedrock of a team’s present and future hopes is shaken — from Medlen, who already had elbow reconstruction surgery in 2010, to the Mets’ Matt Harvey to the NationalsStephen Strasburg and Jordan Zimmermann.

Bryce Harper, Drew Storen and Adam LaRoche of the Washington Nationals share their superstitions and favorite songs. (Whitney Leaming/The Washington Post)

Thanks to “Tommy John surgery,” invented 40 years ago by Frank Jobe, who died last week, hundreds of pitchers’ elbows have been saved. A third of all MLB pitchers last year have had that elbow ligament transplant surgery. But the range of outcomes is wide, from slightly better stuff to lingering problems to the worst fear: a second surgery where data samples are smaller and outcomes less favorable. Not only do all pitchers face a generalized fear, but one-in-three can look at their own scar and wonder “again?”

The Braves will have three-fifths of their projected starting rotation on the disabled list on opening day. Besides Medlen, Brandon Beachy, who had ligament transplant surgery in 2012, has been shut down because of tightness and inflammation in the joint after many of his fastballs Monday were in the low 80s, and Mike Minor is expected to be out at least until mid-April because of a sore shoulder.

Fortunately for Atlanta, one good starting pitcher still remained on the free agent market, Ervin Santana. So, they signed him Wednesday for $14 million for one year. Santana is a workhorse, but he’s not Medlen. Now the Braves have just two established starters to begin their season: Santana and excellent Julio Teheran, 23. Welcome to the National League East.

Phillies star Cole Hamels, 30, is out indefinitely with shoulder/biceps tendinitis. He should be fine. He better be. The Phils still owe him $112.5 million. Legend Roy Halladay retired last winter after pitching with a torn rotator cuff, a frayed labrum and a bone spur in his shoulder. If he were a horse, his nickname would be Glue Factory.

The Mets’ rebuilding hopes are in suspended animation until Harvey returns, presumably next year, from Tommy John surgery.

The Nats’ offseason prize, Doug Fister, was shut down with elbow inflammation last week but “played catch” on Tuesday. The Nats think he’ll be ready for his first regular start in April. That’s good news unless Fister pushes to make his new team happy and turns a barking joint into an actual injury.

The Marlins are in perfect health, but who cares?

Medlen, whose 2.47 ERA is second only to Clayton Kershaw since July 2012, illustrates the endangered existence of his whole breed. In 2012, some argued that the Braves’ rehab method for Medlen, which limited his total innings by using him in the bullpen for four months before putting him in their rotation, was better than the Nats’ innings-limit shutdown of Strasburg. While Medlen pitched the same number of innings, he also pitched a month longer, including a playoff game. Does Medlen’s new injury change any opinions? Or is everyone just best-guessing and good luck to them all?

On Sunday, Medlen knew he was hurt one pitch before everyone else. He felt a pain in his elbow “like being stabbed by a knife,” he said Wednesday. Like all pitchers who’ve had TJ surgery his last wish was to endure a year or more of rehab again. So, he rubbed his elbow and decided to throw another pitch. Or, rather, his emotions demanded it. He had to find out.

“It was a denial, frustration, anger thing,” he told reporters in Braves camp. Before his last curveball reached the plate, he was already walking off.

The Braves now say it is a “high likelihood” he will have another Tommy John surgery.

“I’ve been emotionally preparing myself,” Medlen said. “It’s something I’ve felt before. I think I had all the answers to anybody’s questions in my head when I was walking off the mound.”

A core irony of contemporary baseball is that almost everything can be “stat-ified,” plus plenty that isn’t worth the trouble, while the single most determinative factor in which teams win and which don’t is the least quantifiable: health of arms.

Which MLB teams should worry this year? One factor is reversion to the mean in the health of starting pitchers. No one knows when the bad luck will come, but few teams avoid it indefinitely. Which team had baseball’s best team ERA (3.18), and one of its healthiest starting rotations last year? The Braves, who got 141 starts from their opening day five, plus five more later from Beachy.

The previous year the NL East also turned in large part on rotation health. The Nationals got a remarkable 150 starts from their opening day rotation in their 98-win season. That more than compensated for injuries to everyday players. Last year they got another high total: 137.

There’s good reason why veterans say that a five-man rotation is really made up of eight pitchers. St. Louis proved it last season, winning a pennant with 10 starting pitchers, including 47 starts by pitchers who were 21 or 22 years old.

Will this year’s Braves mirror last year’s Cards? Atlanta’s depth, including youngsters Alex Wood and David Hale, should help until May when Gavin Floyd, acquired in a trade, should be back from . . . yes, his own Tommy John surgery.

In baseball, our pity should not be for teams. As long as there’s been baseball, “you can’t have too much pitching.” And teams that don’t plan for it should blame themselves.

Our sympathy belongs with the exceptional pitcher, such as the gritty Medlen, who evoked some of the artistry of Greg Maddux over his 43 starts the past two seasons. Not many have come back from two elbow ligament transplants, but it has been done. If that’s what Medlen needs, the NL East, and all of baseball, might want to disavow its usual allegiances and root for him.

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