WASHINGTON -- Sometime during the postseason, the Nationals will likely face a slugging left-handed hitter in a key late-inning situation. When this happens, manager Dusty Baker will have to make a vital decision: Which left-handed reliever to call on?
Washington's lefty relief corps has undergone a makeover. For most of the year, the Nats carried three southpaws in the bullpen, but in July and August, Felipe Rivero was traded, Sammy Solís got hurt and Oliver Pérez began to struggle. Washington quickly traded for Marc Rzepczynski and Sean Burnett.
Baker said the Nationals acquired those pitchers with an eye toward big-name bats on other National League rosters.
"That's why we brought them in here," Baker said. "We know all those same names that you talk about. … These guys are going to be big in the equation."
The recent turnover has given Baker little time to figure out whom to use when, something he'll have to grapple with in the days leading up to the postseason.
Rzepczynski seems to have established himself as the Nats' best lefty reliever, tossing 10 innings while allowing two earned runs and holding lefties to 2-for-19.
Still, Baker has leaned on Burnett and Perez to get specific lefties out in high-leverage spots, while calling on Rzepczynski to face multiple batters at a time.
Since Rzepczynski showed up Aug. 26, he has faced 40 batters, 21 of them lefties. Burnett has faced 14 batters, 10 of them lefties. Perez has faced 14 batters, 13 of them lefties.

The way Baker has employed Rzepczynski differs dramatically from how he has been used for most of his career. The veteran's five previous teams all viewed him mostly as a matchup specialist. From 2012 through the trade that brought him to Washington, Rzepczynski appeared in 309 games but pitched only 194 1/3 innings.
Rzepczynski's splits mostly support his reputation. Though he's been almost as tough against righties as lefties in 2016, his career splits make him look like a specialist. For his career, Rzepczynski has held lefties to a .222/.291/.297 line, compared to .276/.375/.431 for righties.
In fact, lefty specialists Burnett and Perez both have much narrower splits than Rzepczynski, against whom righties have a career .806 OPS compared to a .588 OPS by lefties, a difference of .221. Righties have a .782 OPS against Perez, while lefties have a .684 OPS against him, for a difference of .098. Righties have a .751 OPS vs. Burnett, compared to a .622 OPS by lefties, a difference of .129.
Based on the numbers vs. lefties, Rzepczynski looks like the most obvious candidate for a high-leverage at-bat against a fearsome lefty hitter.
Then again, Rzepczysnki has stronger numbers against righties this season -- which he ascribes to increased use of his changeup -- and that versatility gives him extra value for Baker and company. The Dodgers, for example, bat lefties Corey Seager second and Adrián González fourth, separated by righty Justin Turner, and the Nationals can gain an advantage by leaving Rzepczynski in to face all three hitters. The Cubs, with lefty Anthony Rizzo surrounded by righties, could present better opportunities for Burnett or Perez.
"In a left-right-left situation, I feel like I can go get any righty out that I need to," Rzepczynski said recently. "I definitely like going out in that situation so we don't have to burn another guy."
With Burnett and Perez pitching well in their matchup roles and Rzepczynski serving as a key setup man, the manager sees no cause to mess with a successful formula.
"They're doing pretty good in that skill set, right?" Baker said last week. "So why are you going to change anything?"
As for which lefties will stay with the Nats in October, Rzepczynski will almost certainly be there. But the roster beyond that depends on Solis' health (he's progressing slowly in his rehab from shoulder inflammation) and the effectiveness of Perez and Burnett.
Baker has made clear that he prefers to have multiple southpaws at his disposal, especially when facing lineups with dangerous lefties.
"[Having multiple lefties] gives the manager just more opportunity to bring a lefty in and more matchups," Burnett said. "It seems like that last series against the Braves, every time [Freddie Freeman] got up after the fifth inning, he was facing a lefty."
How far the Nationals advance in the postseason could depend on an at-bat between a lefty slugger and one of Washington's southpaw relievers. Baker has two weeks to figure out which one it'll be.