It took 12 games — no more, no less — for the Washington Nationals’ bullpen to become a puzzle of injuries, usage and concern about how to make it through a long stretch with no breaks. Saturday’s 6-2 win over the Arizona Diamondbacks at Nationals Park was the tipping point.

The Nationals were sharp at the plate, logging 15 hits, and Erick Fedde finished five innings with nine strikeouts to match a career high. But the afternoon included Wander Suero walking off the field with head athletic trainer Paul Lessard. Manager Dave Martinez said afterward that Suero grabbed his left side and the team didn’t want to risk anything. Suero, who faced two batters and threw 13 pitches, was set to undergo an MRI exam Saturday. The Nationals expect to know more about his status Sunday morning.

The bullpen has been taxed by recent short outings by Stephen Strasburg and Patrick Corbin. Before his team beat the Diamondbacks and before Fedde threw the first of his 95 pitches, Martinez announced that left-handed reliever Luis Avilán tore the ulnar collateral ligament in his left elbow, an injury that typically leads to Tommy John surgery. And after Suero exited his fourth appearance of the week — and his eighth of the young season — a thinned group was at risk of getting thinner.

“It’s always concerning when you have to use your bullpen so much, absolutely,” Martinez said. “But these guys understand the game and they know that they got to pitch; that’s why they’re here. It stinks when you have to go out there when someone’s injured.”

Kyle McGowin rushed out to replace Suero in the ninth. As he did and once Trea Turner booted a grounder that could have started a double play, Daniel Hudson warmed for his third appearance in three games. Hudson never got into the game; McGowin stranded two runners to finish the victory. The problem is the bullpen has needed to cover too many innings in this run of 13 games in 13 days. Take Avilán as the prime example.

The 31-year-old hadn’t topped 37 pitches in an outing since he threw 40 on Aug. 26, 2017. Before that, he hadn’t passed 37 since the first few appearances of his career in 2012. But the Nationals asked him to do so Tuesday (to save other relievers after a four-inning start by Strasburg in a loss at St. Louis) and Thursday (to save other relievers after a two-inning start by Corbin in a loss to Arizona). On Tuesday, he needed 38 pitches to complete a crooked inning. On Thursday, he used 39 pitches to record six outs.

Following that second appearance, Avilán told Martinez he felt discomfort in his elbow. He soon went on the 10-day injured list with left elbow inflammation and McGowin was promoted in his place. But on Saturday, Martinez told reporters Avilán had torn his UCL.

Avilán made the team as a nonroster invitee to spring training and made four appearances in the Nationals’ first 10 games. Sam Clay, now the only left-handed reliever aside from closer Brad Hand, gave up a solo homer to Eduardo Escobar in the sixth inning Saturday. Martinez turned to Clay, Kyle Finnegan, Tanner Rainey, Suero and McGowin (as an emergency option) to relieve Fedde.

“He’s going to weigh his options,” Martinez said of Avilán choosing to undergo surgery or see if he can heal without it. “I feel awful as we always do when somebody gets hurt. But we wish him well and wish him a quick recovery, whichever way he decides to go.”

The Nationals are also still without Will Harris, who is recovering from right hand inflammation and throwing bullpen sessions at the team’s alternate site in Fredericksburg. But as it always goes, they plugged the holes and kept playing.

Fedde struck out six of his first nine batters and received a mixed bag from the defense behind him. Center fielder Andrew Stevenson dropped a flyball on the warning track in the first. Two innings later, Turner mistimed his jump for a soft liner and let a single nick off the top of his glove. The miscues put eight extra pitches on Fedde’s arm. Yet he was helped by the offense — including three hits apiece from Turner, Yan Gomes and Kyle Schwarber — and a strong throw and tag to nail Tim Locastro in the third.

Locastro, the Diamondbacks’ speedy center fielder, had set a major league record with 29 successful steal attempts to begin his career. After he took off against Fedde, Gomes skipped a throw and Starlin Castro touched Locastro’s back before his hands could reach second base. The out was even bigger after Kole Calhoun homered on the next pitch. Locastro then exited with a dislocated left pinkie finger.

“I feel like I can throw any pitch in any count and be effective,” Fedde said. “When you have that feeling, it’s really easy to be confident and attack the zone.”

His nine strikeouts showed the diversity of his arsenal: four with his sinker, three with his curve and two with his change-up. On his way off the field in the fifth, he was embraced by Gomes before walking through a line of fist bumps in the dugout. Every one was earned.

In his past two starts — in place of Jon Lester, the club’s expected fourth starter — Fedde has lifted Washington by scattering two runs across 9⅔ innings. That they have come with Corbin struggling is even bigger. But what discouraged Saturday was having Suero exit early. He had appeared Tuesday, Wednesday and Thursday, totaling 36 pitches. He had pitched well, too, having yielded three hits and a run in 6⅓ innings this season.

Now the Nationals will just hope he can pitch again soon.

More from The Post: