WEST PALM BEACH, Fla. — This begins with Carter Kieboom. Because of all the Washington Nationals have to address in the coming weeks — their infield, their fifth starter, the final spots in their bullpen — how Kieboom looks, and how much confidence he inspires, can keep a short list of questions from growing any longer.

The Nationals will carry 13 position players on an expanded 26-man roster. If Kieboom makes the team out of spring training and earns regular work at third base, he would be the 13th and final player, joining catchers Yan Gomes and Kurt Suzuki; infielders Howie Kendrick, Ryan Zimmerman, Eric Thames, Starlin Castro, Asdrúbal Cabrera and Trea Turner; and outfielders Juan Soto, Victor Robles, Adam Eaton and either Michael A. Taylor or Andrew Stevenson. But if Kieboom doesn’t, and he has to cook a little longer in the minor leagues, this gets more complicated.

Washington hopes Kieboom can take the next step, play third and, by doing so, help fill the void left by Anthony Rendon. Its ­rotating infield could also put ­Cabrera, Castro or Kendrick in that spot, and it’s likely that all three will get reps there in West Palm Beach. But the best version of the Nationals would have Kieboom, a top prospect, a 22-year-old who struggled through 11 games last year, coming into his own. But that 11-game stretch of 2019, in which Kieboom replaced an injured Turner at shortstop, raised concerns about his bat and defense.

The club’s pitchers and catchers will report to its facility here Wednesday. Their first full workout is Thursday. Then position players report Monday, the first full-team workout is the following morning, and Kieboom will be on the clock. If he begins the season at Class AAA Fresno, the Nationals probably would fill out their roster with Wilmer Difo, Adrián Sanchez or Emilio Bonifacio, a veteran utility player who has a nonroster invite to spring training. That’s a decision they would rather not make.

After Kieboom, and how the infield could form around him, Washington’s most pressing need is a solidified fifth starter. For the next six weeks, from now until Opening Day, Joe Ross, Erick Fedde and Austin Voth will be locked in an internal competition. Each of the three pitchers had a chance in the rotation last season, whether it was as the fifth starter or in place of Max Scherzer while he battled injuries. And, throughout the year, each of Ross, Fedde and Voth flashed the potential to join the rotation full time.

Ross was making consistent starts before he underwent Tommy John surgery in July 2017. His best stretch of 2019 came in August, when he had a 1.05 ERA in five starts. His worst was in the spring, when the Nationals tried him in the bullpen, his command slipped, and he was entirely ineffective. When Ross is going well, he is working inside with his sinker, putting away hitters with his breaking ball and can mix in his change-up. When he isn’t, his issues stem from a lack of fastball command, which is common among unproven pitchers.

Fedde shined last spring once Jeremy Hellickson went to the injured list, and he also had a solid run in August. But his success was short-lived, and always has been, because of fluctuating command. Voth had a small handful of standout starts and showed an ability to miss bats with a fastball-curveball combination. But his problem was health: He dealt with a blister on his right index finger and, more seriously, right shoulder tendinitis.

One of them will join a staff of Scherzer, Stephen Strasburg, Patrick Corbin and Aníbal Sánchez. Another is expected to round out the bullpen. With a bigger roster this season, the Nationals will have both a five-man bench and an eight-man bullpen. The definite members of that bullpen are Sean Doolittle, Will Harris and Daniel Hudson. Tanner Rainey and Wander Suero seem to be safe bets, too, but both righties have minor league options and could be sent down to begin the year without being placed on waivers.

Rainey and Suero would leave three more spots. The most logical options are Hunter Strickland, Roenis Elías and whoever does not make the rotation among Ross, Fedde and Voth. An added layer is that Voth and Ross are out of options, meaning only Fedde can jump between the majors and minors without going on waivers each time.

Other 40-man roster relievers include Kyle Finnegan (signed to a major league deal in the offseason), Ryne Harper (recently acquired in a trade with the Minnesota Twins), Austen Williams, Aaron Barrett and James Bourque. Relievers with ­non-roster invites to camp include Fernando Abad, Kevin Quackenbush and Javy Guerra, who was a non-rostered member of the World Series team.

Some combination of these names will complete the Nationals’ roster by the end of March. That could mean Kieboom at third, Ross in the rotation and Elias, Voth and Strickland in the bullpen. Or maybe it will be Difo or Sanchez instead of Kieboom, Fedde taking one of two roles, and a developing reliever, perhaps Williams, making his case. Or maybe there will be a complete surprise, such as when infielder Jake Noll raked last spring and had a locker and uniform on Opening Day.

That’s now up to the players to decide.

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