Aaron Barrett, shown at the Nationals’ spring training complex in February 2016. (Jonathan Newton/The Washington Post)

A homegrown Washington Nationals reliever watches every game from a couch hundreds of miles away from where his former fellow relievers struggle, and what seems like a lifetime away from the days when he could have helped them. Right now, Aaron Barrett can only wait.

No one knows for sure what will happen if he doesn’t wait, if he starts throwing again. The doctors have never seen an injury like his before.

Renowned orthopedic surgeon James Andrews, who has performed and overseen hundreds of elbow surgeries on major leaguers, thought Barrett must have gotten hit by a car. Throwing a baseball never caused so much torque.

But throwing a baseball in July 2016, harder than he had at any point since his Tommy John surgery in September of the year before, is precisely how Barrett broke his humerus. The same motion he has made hundreds of times is the one that sent Barrett’s elbow (and career) flying into uncertainty.

But it is also the motion he will use to get back to the big leagues, if he has his way. Since suffering one of the most gruesome elbow injuries in Nationals history, Barrett has been unwilling to accept any other plan.

“I questioned ‘why me?’ for a long, long, long time,” said Barrett, 29, who over two seasons with the Nationals appeared in 90 games, the last in August 2015. “Now, it’s like, why not me. Why not me be the first person to ever do this? I just keep telling myself, this is going to be the most amazing comeback story anyone has ever seen.”

Unfortunately, the extent of a comeback generally has a direct correlation to the extent of the fall, and Barrett’s was hard, swift and loud. He was rehabbing from Tommy John surgery, pitching a simulated game at the Nationals’ spring training complex in Viera, Fla., when players conditioning a few fields over heard a crack so loud they thought they heard a gunshot. It came from Barrett’s arm, an injury so devastating it left fellow pitcher Mat Latos vomiting in the dugout after he saw it.

Barrett, in what he called the most excruciating pain of his life, ran around the mound holding his elbow until trainer Jon Kotredes could corral him, hurry him to a private room off the training room and figure out what to do.

Kotredes called Barrett’s wife, Kendyl, and they hurried to an emergency room. Barrett was still in uniform, Kotredes certain he had snapped his humerus. The ER doctor, not drawing conclusions from the baseball pants and jersey, asked how Barrett hurt his arm. Then the doctor started laughing at the answer. You can’t break an arm this badly by throwing a baseball.

“He said, ‘He probably just tore his ligament again. Either way, he’s screwed,’ ” recalled Barrett, who was on pain medications at the time and therefore took the unorthodox step of trying to kick the man for his pessimism.

“I was so pissed. I was like, you’ve got to be kidding me,” Barrett said. “That just started the week to come.”

The break happened on a Friday. Andrews could not see him until Monday in Pensacola, Fla. Kotredes thought flying would endanger Barrett further, perhaps causing complications with the swelling. So he, the Barretts and their beloved dog, Trigger, piled into a car and drove seven hours to meet with Andrews.

Barrett was in surgery later that day, as Andrews wanted to repair the bone before clotting could potentially set in. As he and his staff tried to drill screws into Barrett’s arm to pull the bone back together, they found themselves replacing drill bit after drill bit. Andrews had never encountered bone so hard.

“They had to replace the drill bit 16 different times,” said Barrett, whose X-rays reveal a bone with 16 screws in it, some that only reach halfway across for reasons Andrews never could tell him. Bone density scans and bloodwork all came back normal, but something about his elbow just wasn’t.

The aftermath was agonizing. Pain blockers that were supposed to last 12 hours lasted three. A pain pump leaked all over Barrett. An anesthesiologist had to leave his anniversary dinner to help relieve Barrett’s excruciating discomfort. It took until the following Thursday for the Barretts to head back to Viera. The next day, hoping for a sense of normalcy, they took Trigger for a walk near Space Coast Stadium. The dog ate a poisonous oleander plant and spent the night in the emergency room.

Said Barrett: “That, as far as breaking yourself down to the very bottom . . . I told my wife, if we can get through this, we can do anything.”

He hopes “anything” includes a comeback, though early rehab was slow and painful. Barrett has picture after picture of Trigger lying next to him on the training table, aware something was wrong with his owner, unwilling to leave his side.

Barrett worked his way up to throwing this winter until a CT scan showed everything was not quite as healed as X-rays made him believe. Doctors told him that, if he continued, he might break his arm again, never pitch again and lose quality of life, too.

So Barrett stopped throwing, which made pursuing a free agent contract difficult after he was waived in October 2016. While he said several teams reached out, none knew what to make of him. Major league front offices know what to expect from pitchers who are rehabbing from Tommy John surgery. No one, including Barrett, knows what to expect with this injury.

The Nationals signed him to a two-year minor league deal this past March, betting on the future, allowing Barrett to stay with the only organization he has ever known. He rents in West Palm Beach, living with Bryce Harper’s brother Bryan, a Nationals minor league reliever who is rehabbing from Tommy John surgery.

Barrett works out six days a week, with treatment, lifts, everything except throwing. For now, he simulates the motion with a ball in a sock. The Nationals’ training staff decided they would wait until a year after his surgery, the second week in July, to allow him to start throwing again.

“There’s no book on this one,” Kotredes said. “But like we tell all our players, your body will tell you when it’s ready.”

Barrett’s mind is telling him he is ready, but not like it used to. Seeing his career grounded helplessly gave Barrett a chance to reset, to appreciate. Most players talk about appreciation gained after injuries like his. But Barrett has also found freedom in a simple goal.

“You have choices in life. If you’re going to choose, why not always choose the positive side?” Barrett said. “. . . I feel like if you look at it on the positive side, you’re going to have a more positive outcome in the long run.”

Barrett has counted it out. He knows that if he begins throwing in July, he should be ready for next season, a season he is grateful the Nationals guaranteed him. But he can’t help but wonder if he might be able to get back sooner.

For now, he can’t risk the rush. For now, he must wait. Andrews still can’t tell him why the break happened like it did or how one pitch caused so much strain. A biomechanic specialist thought only a jump in velocity of 8 to 10 mph could have caused so much damage, but if Barrett was throwing 95, that means he must have jumped to . . . no, that can’t be.

Barrett doesn’t think he threw 105 that day. But he does believe in the potential of what he describes as a bionic arm, complete with new ligament and newly enforced bone he hopes will lead to a long career ahead. Soon, he can start the throwing program that will get that career back on track. Until then, all he can do is watch and wait.