Nationals starting pitcher Dan Haren delivers a pitch through the shadows against the Tigers. (Jonathan Newton/The Washington Post)

During a rocky and uneven first month of the season, the Washington Nationals pleaded for patience, vowing their talent and potential would shine through. Over the past three series, capped by Thursday’s 5-4 win over the defending American League champion Detroit Tigers that made for a two-game sweep, the Nationals have looked more like the team worthy of the lofty expectations bestowed upon them before the season.

The Nationals limped through the first month as barely a .500 team. But they have found themselves in the past three series against the Atlanta Braves, Pittsburgh Pirates and Tigers, moving four games over .500 with six wins in nine games.

Dan Haren, without his best stuff, held down one of the most fearsome lineups in baseball for six innings. The offense, powered by Ryan Zimmerman and Adam LaRoche, singled Tigers starter Doug Fister to death in three innings. Well-rested relievers Ryan Mattheus and Drew Storen preserved a one-run lead. And closer Rafael Soriano pitched the ninth to notch his 12th jersey-untucking save.

“This is what we did last year,” Manager Davey Johnson said.

“We knew it was a matter of time before this lineup and this staff gets going,” LaRoche added. “And people are just starting to see that. I don’t think we’ve scratched the surface yet.”

The Post Sports Live crew discusses whether the Nationals are turning a corner and playing better or if it is too soon to tell. (Post Sports Live)

The Tigers came to Washington with one of the most potent offenses in the majors, racking up more than five runs a contest. Against the Nationals, they mustered only five runs in two games, three of them coming on one swing in the sixth inning, the sole glaring mistake made by Haren.

To some players, the brief series felt more like fall than spring.

“We played the games like it was that kind of [World Series] atmosphere,” Tigers catcher Alex Avila said. “We were pretty excited to play, and they were two really good games. The thing is, we’ve both been playing well up to this point. So if that continues, it could happen.”

Said Haren: “Everyone was really excited for this series to begin with in the clubhouse. It’s always fun playing a team of that caliber. You get fired up to see guys like [Miguel] Cabrera and [Prince] Fielder and everyone in the clubhouse was excited for it.”

Pitching on six days’ rest because of Monday’s off day and Tuesday’s rainout, Haren said he felt like he was without his best stuff and was constantly searching for ways to put batters away. He wiggled through five innings of hits and hard outs, allowing the top four hitters of the lineup to go only 2 for 12 against him.

In the sixth, holding a 5-1 lead and facing the bottom of Detroit’s lineup, Haren stumbled. He walked Jhonny Peralta, and then Omar Infante reached on a bunt single. Haren then left a cutter over the plate to pinch hitter Matt Tuiasosopo that was hammered over the visitor’s bullpen in left field, trimming the deficit to one run.

Fortunately, the Nationals’ offense had given Haren and the bullpen a cushion. They pounced on Fister in the first two innings. Five of the first six batters had hits, starting with Denard Span’s double. Roger Bernadina, Zimmerman, LaRoche and Ian Desmond singled as part of the three-run first.

The Nationals again tormented Fister in the second, tacking on two more runs with walks and singles. Span was hit by a pitch and Bernardina, starting for a still injured Jayson Werth, drew a walk. Singles by Zimmerman and LaRoche drove in the runs, and staked Haren to a 5-1 lead. Fister departed after three innings. Zimmerman had his second three-hit game of the season.

Johnson called on Mattheus for the seventh, working for the first time in six days, a byproduct of stellar pitching performances by the starting rotation and matchups. Mattheus’s scoreless frame included one hit, but also a strikeout of Cabrera, the reigning AL MVP, on five pitches.

Storen, who pitched once in the past nine days, fired a scoreless eighth inning that included some drama. With Avila on first base with two outs, pinch hitter Don Kelly lifted a ball to left field. Tyler Moore raced and dived in foul territory, but the ball popped out of his glove, a potential third out. Storen then induced a deep flyout to right field that, for a moment, made the announced crowd of 28,742 hold their collective breath.

Soriano injected more drama in the ninth after giving up a two-out single to Cabrera. Johnson had already decided that if Cabrera knocked a double he would intentionally walk Fielder. On the second pitch of the at-bat, Fielder lifted a ball to deep center field that kept pushing Span back toward the wall. When it settled in his glove, the Nationals celebrated.

“Everyone in this room will tell you that we didn’t play great baseball at the beginning of the season,” Zimmerman said in a decidedly upbeat clubhouse afterward. “Defensively we were sloppy, offensively we were very inconsistent. Even the pitchers weren’t that great at the beginning. But you’re going to go through things like that in a season and when it happens at the beginning obviously it’s a little more glaring than if it were to happen in July or August. It’s nice to play better. We’ve just got to keep doing what we’ve been doing lately.”