Sammy Solis is one of a handful of lefties competing for spots in the Opening Day bullpen. (John Bazemore/Associated Press)

WEST PALM BEACH, Fla. — The Nationals have 10 Grapefruit League games to go, 10 games to get careful regulars their work, 10 games to get relievers in shape, 10 games to stretch their starters’ outings to regular season length. They have 10 games, plus the exhibition game in Washington, to whittle a spring training roster of 45 to a regular season roster of 25.

That Opening Day roster can change hours after their season opener March 29. General Manager Mike Rizzo hinted that the roster his team uses in the first week of the season — which contains two off-days in a three-series span — could be different than the one on which he settles for more grueling stretches. But for the most part, he doesn’t expect to be particularly manipulative.

“I don’t know what we’ll exactly do with the Opening Day roster because we have so many off-days around there,” Rizzo said. “but five starters, seven relievers seems reasonable to me. I don’t see us veering off that.”

Five starters and seven relievers means 13 spots left for position players, five for the bench. Here is what we know about who will be those five starters, seven relievers, eight position-playing regulars, and five bench players — barring anything unforeseen. Ten games is plenty of time for the unexpected to arrive, too.

One spot in the rotation is up for grabs, and A.J. Cole will probably get it to start.

The Nationals’ rotation has been a fairly uncomplicated unit all spring. Max Scherzer is in line to start Opening Day. Stephen Strasburg is scheduled to be the No. 2. Tanner Roark and Gio Gonzalez will slot in somewhere behind them. Only the fifth spot remains unsettled, and everyone has suggested all along that right-hander A.J. Cole will get a chance to take it.

Rizzo said fellow right-hander Erick Fedde, who is only a year younger than Cole, is also in contention.

“He’s coming in fresh now. He’s feeling good about himself. But the way he’s pitching now is how I expected him to pitch,” Rizzo said Thursday. “We see him as a mid-rotation guy, and the stuff he’s featuring continues to allow us to believe that.”

For now, despite missing a start due to illness and having to make it up in a minor league game, Cole is the favorite to be that fifth starter when the season begins.

The most heated competition is among left-handed relievers.

Most of the bullpen is set. Sean Doolittle, Ryan Madson, Brandon Kintzler, Shawn Kelley, and Joaquin Benoit are all guaranteed money, and will almost certainly get a chance to prove they deserve it to start the season. That leaves two spots — the ones that normally go to middle-relief lefties. Sammy Solis is the only legitimate lefty contender who has options left, meaning he is the only one the Nationals can cut without the risk of losing him on the waiver wires. The complication: The Nationals have always viewed Solis as their best homegrown left-handed weapon, and he seems to be a few steps ahead of the pack.

The Nationals are stretching out Matt Grace to make him more able to handle long relief, a role the Nationals would not have covered if Solis joined the other five in their bullpen. Grace could provide long-man capabilities as well as the ability to get a single lefty out, which might make him the best fit for a bullpen that isn’t exactly built to eat bad starts and lots of innings.

But hard-throwing Enny Romero and veteran left-hander Tim Collins are also in the mix. Collins is in camp on a minor league deal, so he could start in the minors, build up, then earn a call-up at a moment’s notice. Romero, however, would have to clear waivers before heading to the minors. The Nationals might lose him in that process. They must consider all of this as they choose.

If Victor Robles is on the roster, he will be starting in the outfield.

“We will not keep him on the bench,” Rizzo said. Given that the Nationals expect Gold Glove finalist Michael A. Taylor and left fielder Adam Eaton to be healthy in plenty of time for Opening Day, that means Robles will probably begin in the minors. He certainly won’t bump Bryce Harper from a starting role.

Without Robles on the bench, Brian Goodwin likely becomes the fourth outfielder, joining backup first baseman Matt Adams, do-it-all infielder Wilmer Difo, veteran Howie Kendrick, and a backup catcher on that bench. Either Difo or Kendrick will have to start at second base until Daniel Murphy’s knee has fully recovered, meaning an infielder such as Matt Reynolds could get an early season chance on the bench.

Miguel Montero is handling the pitching staff like he is going to make the team.

If Miguel Montero didn’t have a legitimate shot at being the Nationals’ backup catcher — or, for the conspiracy theorists, if the Nationals weren’t already planning for him to take that job — they probably wouldn’t be quite so determined to get him innings with all of their starters. Montero was part of a meeting with Strasburg and Matt Wieters in which the trio discussed Strasburg’s strategy, then Montero caught him on the back fields, a process Strasburg said helped their comfort levels grow. Montero has caught Roark repeatedly, and continues to make the rounds of Nationals starters as Dave Martinez and his staff try to help him build rapport with all their starters.

Sure, Pedro Severino doesn’t need as much time to build those relationships, having had years. But the deliberate nature of Montero’s tour of the pitching staff, as well as his recent tendency to hit line drives at the plate, indicate he is putting himself in position to serve as the backup.

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