© 2014 MLB Advanced Media, L.P. All rights reserved.

8/17/2014 6:33 P.M. ET

Stammen proves his value in walk-off win

WASHINGTON -- Lost in the Nationals' impressive come-from-behind, walk-off victory over the Pirates on Saturday night was yet another stellar outing from reliever Craig Stammen.

After a shaky five innings from starter Gio Gonzalez -- the left-hander surrendered three earned runs, seven hits and two walks on 102 pitches -- Stammen fired three scoreless frames to provide the Nationals with an opportunity to stage a rally in the eighth, which Adam LaRoche capped off with a game-tying two-run blast.

It was the second time in his last three appearances that Stammen allowed no runs on one hits over three innings as part of a Washington walk-off win. On Aug. 7, the right-hander held the Mets without a run in the 11th, 12th and 13th innings before Bryce Harper ended the game with a home run.

"You can't [quantify his impact]. The guy can go out there for multiple innings," manager Matt Williams said Saturday. "Long guys don't get much credit, but they're really, really important to your team in games like this one. … They're valuable."

Span hasn't heard from Nats on '15 option

WASHINGTON -- Nationals center fielder Denard Span is putting together a career year. He's on pace to break his single-season marks in stolen bases, doubles and hits, all while posting his first .300 campaign since 2009. Still, the leadoff man's future in Washington remains uncertain.

Span is eligible to become a free agent after this season if the Nationals opt not to pick up his $9 million option for 2015. And as of Sunday afternoon, Span said there's yet to be any dialogue between him and the front office regarding next year. Meanwhile, general manager Mike Rizzo declined to comment on the situation.

"I haven't heard anything," Span said. "If I had to guess, I probably would say I wouldn't hear anything until the season's over."

From an outsider's perspective, it appears Span has lost some job security over the past several weeks, as the Nationals called up their top two outfield prospects, Steven Souza Jr. and Michael Taylor. However, the moves were necessitated by injury -- Souza's after Nate McLouth went to the 15-day disabled list because of an ailing right shoulder, and Taylor's after Souza sprained the AC joint in his left shoulder crashing into the wall at Turner Field on Aug. 9.

"It's not something I'm really thinking about," Span said of the recent influx of young outfield talent. "If I do what I'm supposed to do individually, then I'm a firm believer that the game will take care of you. I come here every day and work my butt off. … If it's meant to be for me to be here long term, then that'll be. If it's meant for me to be somewhere else, then that'll be."

If the Nationals were to let Span walk after this season, the center fielder said he would have a positive outlook on testing the free-agent market. After all, it would be his first time going through such an experience, and there would likely be significant interest in his abilities considering his 2014 campaign.

"Most players don't get that opportunity to be a free agent. So whenever you have that opportunity to test that market … it's an exciting feeling for a player," Span said. "Every player wants to maximize their potential and their value in this game."

Nonetheless, that point would become moot if the Nationals decide to pick up Span's option and make him a part of the team's future, at least for 2015.

As for now, Span said his focus is entirely devoted to the final stretch of the regular season. With a convincing lead over the Braves in the National League East, Span understands the Nationals have an opportunity to do something special. And he's not going to let anything deter him, regardless of when the Nationals make their decision.

"I'm not a genie," Span said. "I try not to play player-GM. because in all my years of playing professional ball, whenever you try to guess what they're going to do or try to put together what you think the front office or the GM is going to do, you're always wrong, because they have a tough job. And my job is to play. So that's what I'm concentrating on doing."

Worth noting

Jayson Werth (right AC joint sprain) was out of the starting lineup for the sixth straight game Sunday against Pirates. Williams said Werth's right shoulder felt tender after a full workout on Saturday.

• Souza (left AC joint sprain) swung a bat on Sunday for the second straight day. The outfielder said he plans on taking live batting practice on the field Monday for the first time since his injury.

Daniel Popper is an associate reporter for MLB.com. He also can be found on Twitter @danielrpopper. This story was not subject to the approval of Major League Baseball or its clubs.