PHOENIX — Mark Reynolds was in the Nationals’ clubhouse Saturday morning. His name was written on the lineup card. Ryan Zimmerman’s was not. But for hours before Washington’s game against the Arizona Diamondbacks, the Nationals would not announce a roster move, for reasons still unknown.

When they finally did announce a move, a half-hour before the game, the move came with none of the surprises the delay suggested it might include. Zimmerman moved to the 10-day disabled list. Reynolds was selected from Class AAA Syracuse. The Nationals moved reliever Joaquin Benoit to the 60-day DL to clear a 40-man spot.

“[Zimmerman], the last couple days, he felt the same. We figured we would give him 10 days, get this thing knocked out and calm down,” Manager Dave Martinez said. “Hopefully he’ll take 10 days and come back.”

No one would identify the specific injury hampering Zimmerman, though the team officially labeled it as an oblique strain. The 33-year-old first baseman said three awkward slides and dives combined to leave him in pain he could play through if it were October, but not for five months. He had missed five of the last seven games and both games in Arizona before landing on the DL, retroactive to Thursday. Zimmerman decided not to play much in spring training, a much-discussed decision aimed at keeping him healthy as long as possible. This injury appears to be the product of impact, not something muscular that could have been avoided during training.

“I’ve been kind of dealing with it for a little while. It was trending in the right direction, and then some of those dives kind of made it worse,” Zimmerman said. “It just got to the point where I couldn’t sustain it for five months. I want to give it some time, get it better. I don’t think it should be too long.”

In the meantime, the Nationals have Reynolds, who hit 30 home runs last year for Colorado but did not get offered a major league deal this winter. The Nationals made him a surprise signing last month, a deal made purely to stockpile depth in case of injury — a move that looks prescient in hindsight, though it was informed by Zimmerman’s recent injury history. The Nationals reached out to Reynolds in spring training, but at that time he did not want to sign any deal that did not guarantee him a major league spot. The longtime big league corner infielder has 281 home runs and a .794 career on-base-plus-slugging percentage. At 34 years old, he refused to settle.

He took his kids to Disney. He played golf. He spent all winter being told he could come to spring training and try to make a major league roster.

“That was brutal. Obviously, I felt like I deserved a major league job after what I did last year,” Reynolds said. “. . . I was like, I’m having way too much fun golfing and hanging out with my kids right now to worry about trying to make a team. So I just didn’t sign.”

Then, when the Nationals came back to him, he decided to try. He said he didn’t want to look back a decade from now and be mad at himself for sitting. So, despite the fact that the Nationals had proven big league regulars Zimmerman and Matt Adams ahead of him at first base, Reynolds took the deal. He spent a few weeks in extended spring training in West Palm Beach, Fla., where he took 10 at-bats a day alongside Daniel Murphy. Then he played eight games with Class AAA Syracuse, five of them in left field, readying him to serve in the same role as Adams — except from the right side.

“He’s played the outfield. He can play third. He can play first. He’s a good guy to come off the bench and give us some pop,” Martinez said. “I told him, ‘Hey, [we’ve got] some lefties coming up. You’ll get a chance to play against lefties.’ We’ll try to utilize him the best we can. You know I like using everybody, so he’ll definitely get to play.”

Martinez was asked the inevitable question, one that will continue to come up as Zimmerman’s injury heals. When Zimmerman returns, what will the Nationals do, now that they have two major league-caliber first basemen who could combine for a perfect platoon? Won’t Reynolds also be able to help them then? Martinez wouldn’t bite.

“We’ll see where we’re at,” Martinez said. Eight players on the Nationals’ current 25-man roster were not on that roster on Opening Day. Washington has used 38 players on its 25-man roster this season. All of last season, the Nationals used 49. Planning ahead probably doesn’t do much good.

Reynolds was not in the starting lineup against right-hander Troy Scribner on Saturday afternoon, but he probably will not have to wait long for his first chance. The Nationals’ bench Saturday, still short because they are carrying an extra reliever, consists of Reynolds, Spencer Kieboom, Wilmer Difo and Moises Sierra. Reynolds is probably their most powerful pinch-hit option.

WASHINGTON NATIONALS (22-18)

Trea Turner SS

Bryce Harper RF

Anthony Rendon 3B

Matt Adams 1B

Howie Kendrick 2B

Andrew Stevenson LF

Michael A. Taylor CF

Pedro Severino C

Stephen Strasburg P

ARIZONA DIAMONDBACKS (24-14)

David Peralta LF

Daniel Descalso 3B

Paul Goldschmidt 1B

A.J. Pollock CF

Steven Souza Jr.

Ketel Marte 2B

Nick Ahmed SS

John Ryan Murphy C

Troy Scribner P

Read more on the Nationals: