Dave Martinez and the Nationals open the season against the New York Mets on Thursday. (John McDonnell/The Washington Post)

WEST PALM BEACH, Fla. — The cardboard boxes are being passed around the Washington Nationals’ spring training facility these days, through the clubhouse and coaches’ offices and onto trucks bound north for the spring, summer and, if all goes well, a bit of fall.

The Nationals will soon follow, with Opening Day drawing closer, when they begin the regular season at home against the New York Mets. It has been a relatively quiet spring training in West Palm Beach, but there are still a few roster questions heading into the year. They revolve around three injuries — to outfielder Michael A. Taylor, utility man Howie Kendrick and reliever Koda Glover — and the recent addition of left-handed reliever Tony Sipp.

Glover (right forearm strain) has thrown on flat ground the last few days but will not break camp with the Nationals. Manager Dave Martinez noted that Glover still needs a full spring training before he returns, and the team wants to be extra cautious given Glover’s injury history. Taylor (left knee and left hip sprains) and Kendrick (a mild left hamstring strain) could still be ready to start the season — Martinez said Thursday that he’s “very optimistic” for that. So could Sipp, who is only behind schedule because he didn’t sign with Washington until March 13. Their availability would completely untangle the Nationals’ imminent roster decisions. Their absences would immediately test the team’s depth.

“They know that we got seven days basically before ...” Martinez said of Kendrick and Taylor on Thursday, and his sentence trailed off there. “We’ll see where they are at.”

Taylor was injured while making a diving catch on March 14, and Martinez initially said the outfielder would “miss a significant amount of time.” But he has seemed to progress well since, and on Thursday he took batting practice, stretched out his throwing to a long toss and ran outside for the first time since the injuries. He will be the Nationals’ fourth outfielder this season and had been competing with Victor Robles to play every day in center.

Kendrick is running at 85 percent and also took a significant step on Thursday, facing Sipp in live batting practice. And that was equally important for Sipp, who threw to hitters for the first time this spring and got up to 15 pitches.

Sipp, who told Martinez he felt good after pitching, will now get a day off before appearing in a minor league game so the Nationals can adjust his workload. On Friday, Sipp said he expects to be ready for Opening Day and will remain in West Palm Beach for two extra days so he can continue facing hitters. Washington will assess Taylor and Kendrick on Friday before determining the next phase of each players’ rehabilitation. Martinez wants Kendrick to play at least three or four spring training games before rejoining the Nationals, and those could come in minor league camp after the Nationals leave for Washington. He did not specify a preferred number of appearances for Taylor.

“The very next day, I felt better. Obviously not 100 percent, but I was happy with how I felt,” Taylor said Thursday. “They told me I could wake up the next day and my knee [would] be like a balloon. But I woke up, there was very little inflammation … and I felt like I was walking better and everything. I’m really not surprised with where I’m at right now.”

Here’s a look at the Nationals’ potential 25-man roster if Sipp is ready, and Taylor and Kendrick start the season on the 10-day injured list:

Starting pitchers: Max Scherzer, Stephen Strasburg, Patrick Corbin, Anibal Sanchez, Jeremy Hellickson

Relief pitchers: Sean Doolittle, Trevor Rosenthal, Kyle Barraclough, Matt Grace, Justin Miller, Wander Suero, Tony Sipp

Catchers: Yan Gomes, Kurt Suzuki

Infielders: Ryan Zimmerman, Matt Adams, Brian Dozier, Wilmer Difo, Trea Turner, Anthony Rendon, Adrian Sanchez

Outfielders: Juan Soto, Victor Robles, Adam Eaton, Andrew Stevenson

In this case, Adrian Sanchez replaces Kendrick in a utility role. Sanchez can play first base, second base, third base and some left field, like Kendrick, and moonlight at shortstop if need be. He has one more year of minor league options, so the Nationals can shuttle him between the majors and minors without placing him on waivers.

Stevenson replaces Taylor, since the Nationals would need a reserve outfielder who can play center. Stevenson has appeared in 94 games across two major league seasons, excels in all three outfield spots and also has options.

Sipp can start the year on the 25-man roster and still not pitch for a few games, giving him a few additional days to ramp up. The Nationals open with Max Scherzer Thursday — a good bet for six or seven innings before the bullpen is called upon — and then are off before playing again Saturday. That should allow them to ease Sipp into action, and they could even use Jeremy Hellickson as an eighth reliever if they move up Scherzer and Strasburg’s second starts to keep each pitcher on regular rest. Hellickson, in that situation, could make his first start after Scherzer, Strasburg, Corbin and Sanchez each make two.

“If it’s just going off pure stuff that I had yesterday, then I can definitely face major league hitters,” Sipp said on Friday. “But you also have to do it, as a relief pitcher, you have to be ready to do it every day. And I’m just trying to be fair to Davey, and I want him to just be able to have free rein to use me like any other guy.”

This is some of what the Nationals will juggle for the next six days, until Scherzer toes the rubber and the season lifts off. But there is one certainty, regardless of how Taylor and Kendrick feel, how Sipp’s arm advances, how Washington fills whatever holes it may have: Everyone, injured or otherwise, will be at Nationals Park for Opening Day. Martinez has already decided that.

“I think it’s important for just us, the club, to have them there for the anthem and be with the players if they can’t play,” Martinez said. “They are a big part of our team whether it’s Opening Day or not, so they are going to be there. I would like for them to be there to stand with the boys.”

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