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3/22/2014 6:29 P.M. ET

Espinosa's hard work starting to pay off

VIERA, Fla. -- All spring, Nationals manager Matt Williams and his staff had complimented Danny Espinosa's approach at the plate, even though it wasn't producing positive results on the stat sheet. On Saturday, the numbers finally matched what the coaches have been seeing.

After flying out in his first two plate appearances, Espinosa homered in his last two, including a walk-off shot off the Marlins' Chaz Roe in the ninth inning that gave the Nats a 6-5 win. Both homers came left-handed, traditionally the weaker side of the plate for the switch-hitting Espinosa.

"We can tell him all day long he's right on, he's right where he needs to be," Williams said. "But it helps when they fall in -- or over."

Espinosa is coming off a rough season that saw him play hurt, hit .158 and spend significant time at Triple-A Syracuse. He came into this spring with the opportunity to battle Anthony Rendon for playing time at second base, or at least secure a utility infield role, but was hitting .184 with two doubles and no home runs coming into Saturday.

In the seventh inning, Espinosa drove a pitch from Kevin Slowey over the wall in deep right-center field. In the ninth, Espinosa lined Roe's offering out the opposite way, near the left-field line. Williams didn't see him taking big swings either time.

"He doesn't have to," Williams said.

Said Espinosa, "Both of those I was just trying to stay short to the ball and just be on time and be short. Not swinging as hard as I can, but just short and on time and trying to barrel the ball."

As for the second-base competition, Espinosa said he doesn't know where he stands, nor is it something with which he's concerned. If circumstances dictate, Espinosa suggested he will embrace a backup role.

"I don't know what the opportunity will bring, if that's the situation," Espinosa said. "I'll prepare every day. I'll always prepare and go about my work like I've always done when I've started. I'll take my ground balls, I'll work on my swing, I'll be in the cage and do what I've always done. And if my name's called later in that game for a pinch-hit or if I get a start that day, I'll be ready to go."

Fister takes step forward with strong start

VIERA, Fla. -- Pitchers around baseball have been getting bad health news all spring, with Tommy John surgery a common endpoint. But Nationals right-hander Doug Fister, sidelined the past few weeks with elbow inflammation, took a big step forward on Saturday toward distancing himself from that crowd.

To be sure, Fister still has a ways to go. His start against the Marlins at Space Coast Stadium nonetheless represented a significant milestone, coming 20 days after his only other appearance this spring. After throwing a stellar 3 2/3 scoreless innings, Fister couldn't guarantee that his issues are completely behind him, but he was encouraged.

"It's something I'm trying to take step by step," Fister said. "You can always have problems or you can always just fly right through. So it's a matter of taking care of business and go about things the right way and hopefully things stay right where they're supposed to be."

Fister threw 47 pitches on Saturday, and Nationals manager Matt Williams plans to get him to around 60 in his final spring start. When the club heads north, Williams said Fister might have to stay back and make one Minor League start, but if all goes well, he could be on track to take the ball on April 6 against the Braves, the first time the Nats need a fifth starter. In the meantime, Washington potentially could begin the season with an extra reliever.

"I would say that he's right on schedule," Williams said.

Fister said he felt good despite "knocking a little bit of rust off," as he held the Marlins to two hits, with one hit batter and four strikeouts. His pitches appeared sharp, including his trademark sinker, which induced a double-play grounder in the second inning.

"Command is coming back," Fister said. "Again, a little rusty. But still working on those kinds of things. I'm pleased with where I'm at, but there's still a long way to go before the season, so I've got a lot of work and a little bit of time."

Williams working hard to put together best roster

VIERA, Fla. -- First-year manager Matt Williams will have to make some tough decisions regarding the Nationals' Opening Day roster, and he is not taking that responsibility lightly.

"My sleepless nights right now are consumed with the bench, the 25th guy, the bullpen and all of that stuff," Williams said.

"I've got acid reflux, which is a product of that I'm sure. But that's part of the job. We want to go north with our 25 best guys and compete and certainly win and all of those things. But yeah, it's fun and it's nerve-racking and frustrating and all of that all at the same time."

Williams' decisions all will occur on the periphery of the roster. He must settle on a fifth starter, the last couple of relief pitchers and the last couple of bench players.

While Williams has a deadline in mind, he also knows he might not be able to stick to it. He has to consider what gives him the best roster for Opening Day, March 31 against the Mets in New York, while understanding that circumstances can change quickly after that.

Williams wants to have "the best 25 guys," but he looks at that question through the prism of how he might manage a game. What might Williams be looking for offensively and defensively? Would he be better served to have the last man on the bench possess the speed to pinch-run, or the offensive punch to pinch-hit in a key spot?

"All of those questions arise every day, 100 times," Williams said. "But that's part of making a decision, that's part of the challenge of the job and that's part of the frustration and the love of the job. It all goes into it."

Span looks to hit ground running when season starts

VIERA, Fla. -- In his first year with the Nationals, it took leadoff man Denard Span until the second half of the season to find his way at the plate.

This year, Span is more comfortable in his surroundings and is hoping to hit the ground running much earlier at the plate.

"My timing's getting better each day, pitch recognition is getting better each day," Span said before Saturday's game against the Marlins. "I feel like I'm very, very close to where I need to be.

"This year, I'm just looking for consistency. I want to play consistent ball from start to finish, coming out of the gates and just doing what I've always been capable of doing at a high level, playing at a high level and just being the leadoff hitter I know I can be."

Span hit .263 with a .677 OPS in the first half last year after coming over from the Twins in an offseason trade. He bounced back in the second half to hit .302 with a .750 OPS.

The 30-year-old came into Saturday hitting .324 (12-for-37) this spring, with three doubles and a triple. The only curious thing about his performance is that he hadn't drawn a walk, but Span said he hadn't changed his approach at all.

"I've been having some better at-bats as of late and battling my butt off with two strikes, but I just haven't been able to draw a walk," Span said. "I'm hoping the opposite happens when the season starts. Last year, I had [12] walks in Spring Training, and then once the season started, I didn't walk as much as I was on pace for.

"So a lot of it is just me seeing the ball. My timing is almost where it needs to be, so I'm not worried about it too much."

Williams doesn't want to stop Harper's aggressiveness

VIERA, Fla. -- In the eighth inning of Saturday's game against the Marlins, Bryce Harper collected a Donovan Solano double not far from the left-field warning track at Space Coast Stadium and unleashed a majestic throw toward home. It was an impressive display of arm strength, but it still was too late to get the runner at the plate and allowed Solano to move up to third.

What was the reaction of Nationals manager Matt Williams?

"Wow," Williams said. "Wrong move, but wow."

Harper's heave encapsulated the 21-year-old's immense ability -- and his tendency to force plays at times, whether it's on the field or on the bases. Williams does want to keep the runner at second base in such a situation, but he also doesn't want to eliminate Harper's aggressiveness at the expense of compromising his talent.

"He comes up, and most guys go, 'Well, there's no chance for me to throw him out at the plate,'" Williams said. "His brain goes, 'Well, I've got a chance.' So that's what young, special talent does. We'll take the good and the bad and move forward into tomorrow and run him out there again."

Worth noting

• Williams has had at least four players volunteer to serve as an emergency third catcher. Two of those, Bryce Harper and Jayson Werth, are former catchers, but Williams isn't planning to let them anywhere near the plate. Two others, Danny Espinosa and Tyler Moore, are more realistic options in a worst-case scenario.

• As for another emergency situation, Williams said that under the right circumstances, he would consider using a position player to pitch. That's something his predecessor, Davey Johnson, never did.

"If the game's completely out of reach and we're taxed in our bullpen, there may be a need for that," Williams said. "And again, we look at winning today's game, but if there's simply no chance we can win today's game, I don't want to cost us tomorrow's game, too."

Andrew Simon is a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB. This story was not subject to the approval of Major League Baseball or its clubs.