WASHINGTON -- A unit that has faced questions all season long is now the Royals’ strength, and it couldn’t be happening at a better time.

The bullpen once again locked things down Thursday afternoon at Nationals Park, tossing four scoreless innings in the Royals’ 7-4 win over the Nationals to finish off a series sweep and head into the final weekend of the regular season with a three-game winning streak.

Royals relievers didn’t allow a run to the Nationals all series. They have now thrown 19 2/3 consecutive scoreless innings dating back to Saturday against the Giants.

“As a starter, we want the ball as long as we can and go out there to finish the job, but it’s been really impressive the way they’ve come in for tough situations, in tight games, and holding it exactly where it is,” starter Michael Wacha said after allowing four runs (three earned) and exiting after five innings in a 4-4 tie. “They’re carrying it right now.”

Kansas City (85-74) remained tied with the Tigers in the American League Wild Card standings after Detroit rallied to beat the Rays on Thursday afternoon. They lead the Twins by three games after Minnesota's 8-6 loss to the Marlins on Thursday night, and the Royals can clinch a postseason berth Friday with a win over the Braves or a Twins loss to the Orioles.

For all the struggles the Royals’ offense is trying to work through, the pitching has constantly kept them in games, and it did again Thursday, courtesy of the bullpen. The Royals and Nationals traded runs in the first – when Maikel Garcia’s dropped popup at second base turned into an unearned run against Wacha – and Hunter Renfroe’s game-tying homer in the second. But Kansas City got six consecutive baserunners (one walk and five singles) against Patrick Corbin for a three-run lead in the third.

Wacha lost that lead when he allowed a three-run homer to Luis García Jr. in the bottom of the frame, and the Royals managed just one baserunner from the fourth to the eighth innings.

Pitching for the third consecutive day for the first time in his career, lefty Angel Zerpa needed just eight pitches to get through a scoreless sixth inning. John Schreiber handled the seventh. Kris Bubic got through the eighth unscathed, and Lucas Erceg -- also pitching for the third consecutive day, a first for his career -- notched his 14th save of the season in the ninth and third in the past three games.

“It’s just open communication with me and the coaching staff,” Erceg said. “I felt fine after the last couple of days. I think I’ve kept my pitch count pretty low and efficient, so that’s kind of step one. I’m just taking it day by day and seeing how I feel and making sure I’m ready to go.”

Before Thursday’s game, manager Matt Quatraro said he was “absolutely” more open to using his relievers three days in a row given how meaningful the games are this time of year. He’s not going to use his high-leverage pitchers every single day if they’re not able to pitch, but the efficiency of recent outings helps.

Zerpa has thrown 34 pitches across three innings the past three days. Erceg has needed 35.

“These guys understand: We came this far, we know what’s at stake,” Quatraro said. “It is a lot to ask of them to go three days in a row, but they’ve been so efficient. … And it is a lot. I’m not trying to downplay that, but they know and they want to be out there.”

The Royals were able to break through in the ninth and get Erceg into the game when MJ Melendez drew a pinch-hit walk, followed by pinch-runner Dairon Blanco’s delayed steal, Michael Massey’s walk and pinch-hitter Kyle Isbel’s sacrifice bunt to put runners on second and third with one out.

Pinch-hitter Adam Frazier lined a two-run single through the left side of the infield.

“We’d like to take the pressure off of [the pitching] at some point,” Frazier said. “But they’ve been really good. Everybody knows what’s on the line, so they come in prepared and try to pick each other up. Everybody wants to be the guy who wants to get the job done.”

With the Royals so close to October, their relievers are ready for anything.

“And I’ll be ready for a fourth day,” Zerpa said with a smile.