NEW YORK -- The Nationals had been playing without a natural first baseman on the roster for about two weeks, since Matt Adams strained his left shoulder making a diving play at first base. Adams had been sidelined for 15 games, but after going through a full pregame routine and crushing the ball in batting practice, he was reinstated from the injured list for Wednesday’s game against the Mets. Adrian Sanchez was optioned to Double-A Harrisburg to create room on the roster.

Adams was in the lineup and batting fifth in his first action since May 4. He returns without a Minor League rehab assignment, however, after he came through his pregame routine looking sharp. Even so, there might have been some rust to shake off, as he committed an error in the first inning on a grounder off the bat of Robinson Cano. He went 1-for-4 with a pair of strikeouts in Washington's 6-1 loss.

“He looked good, he felt good, he saw some velo, which for him, it’s all about getting ready for the fastball,” manager Dave Martinez said prior to the game. "He said he was ready. And then, like I said, I watched him take batting practice yesterday, I watched him run around, fielding, throwing everything. He looked really good.”

Adams got off to a bit of a slow start this season, batting .250/.269/.469 with three home runs and an 89 OPS+ in 29 games. He was signed by the Nats to be their primary left-handed pinch-hitter, but an injury to Ryan Zimmerman forced him into everyday action.

Even though Adams missed two weeks, he did not feel the need to see live pitching in the Minors, because pitching machines simulated velocity, and he had been fielding grounders consistently.

“I’m in every inning, watching the game, just keeping my mind sharp that way,” Adams said about staying focused while on the IL. “Putting myself out there on defense in those situations. And in the box, I think hitting is just the timing perspective.”

Without Adams, the Nationals used a combination of Howie Kendrick and Gerardo Parra at first base. The veterans have been serviceable, but having Adams back gives the Nationals another power hitter the lineup has sorely missed.

“It helps our bench a lot,” Martinez. “Now all of a sudden, Howie’s not starting today, so you’ve got Howie, you’ve got Parra, [Kurt] Suzuki. … Our bench is pretty strong right now.”

Rosenthal’s rehab assignment to continue

The line from Trevor Rosenthal’s latest Minor League rehab assignment was not encouraging -- two runs on one hit with two walks, a hit batter and a wild pitch as he tossed an inning-plus for Harrisburg on Tuesday night.

It was the fifth rehab outing for Rosenthal, who is on the injured list with a viral infection, although the Nationals are hoping he can use his time in the Minors to iron out his mechanical issues and acquire some confidence. But the results have not improved much. In five appearances, he has given up three runs in 4 1/3 innings.

Rosenthal, who will take a day off on Wednesday, needs at least one more rehab appearance, according to Martinez. He added that the team does not believe Rosenthal has the “yips” but that his issues are strictly mechanical ones that the Nats hope he can work his way through.

“I’m not so worried about his line as far as giving up hits, runs or anything, it’s more about strikes and being consistent,” Martinez said. “If his misses are up and down, those are normal. We just don’t want him yanking pitches, and apparently, yesterday he yanked a few pitches.

“We just want to hone in on his mechanics and make sure everything’s clean so that when he comes back, he’s back. We want Rosenthal back. We need Rosenthal, but we want him back to help us win games and help our bullpen.”

Worth noting

Left-hander Dan Jennings has opted for free agency after being designated for assignment earlier this week.

When a player's contract is designated for assignment -- often abbreviated "DFA" -- that player is immediately removed from his club's 40-man roster, and 25-man roster if he was on that as well. Within seven days of the transaction (it was previously 10 days), the player must either be traded, released or placed on irrevocable outright waivers.