Jayson Werth of the Washington Nationals reaches for first base, but is thrown out. Werth finished with two hits, including a three-run homer. (Patrick Smith/GETTY IMAGES)

In the previous game, before a raucous crowd at Nationals Park, Jayson Werth did what has come to be expected from him in the first year of his gigantic contract with Washington. He struck out three times — twice looking — against his former team, the Philadelphia Phillies. The third-largest crowd in stadium history booed, which might have caused one to wonder: Were the catcalls coming from fans of his former team or his current one?

On Monday against the Arizona Diamondbacks, Werth turned in a completely different performance. He collected two hits, including a three-run homer to the opposite field in the fourth inning, to power the Nationals to a 4-1 win behind a strong start from left-hander Ross Detwiler.

Under the weight of his new contract and the enormous pressure that ensues, Werth hasn’t been himself much of his first year with the Nationals. At times, he has talked about how his struggles have made him feel and how he has worked to improve. And every time he mustered a strong performance, fans wondered if Werth was finally breaking out of his long slump.

This time, following his 2-for-4 night before an announced crowd of 19,377, Werth insisted he felt like he has found his swing. Against Diamondbacks left-hander Joe Saunders, a graduate of West Springfield High, Werth was keyed in from the start. After the game, the 6-foot-5 right fielder admitted that recent work in drills have “helped me come back inside the ball.”

In the second inning, Werth drove an 83-mph pitch from Saunders into the left field corner, just in front of the foul pole, for a double. After Danny Espinosa drew a walk, Jonny Gomes drove a pitch into the right-center field gap, driving in Werth and giving the Nationals a 1-0 lead.

Ryan Robertsof the Arizona Diamondbacks warms up before leading off against the Washington Nationals in the second inning. (Patrick Smith/GETTY IMAGES)

“I think the past week, 10 days, whatever, really locked it in,” Werth said. “It was a struggle really to find it. Been a long time coming. I knew where it was. I just didn’t really know how to get there. Finally, I feel like I got there.”

Two innings later, Werth again hit Saunders hard. After Ryan Zimmerman singled up the middle and Michael Morse drew a walk, Werth drove a pitch into the stands behind right-center field for a three-run home run and a 4-0 Nationals lead.

“I said maybe three weeks ago I thought he was coming along,” Nationals Manager Davey Johnson said. “Every day I see more of Jayson Werth come out.”

With the win, the Nationals pulled within two games of .500 and stayed in third place in the National League East. The Nationals (62-64) have won their past two series, including the weekend’s three-game set against the Phillies, baseball’s best team. So holding their own against the NL West-leading Diamondbacks (69-59) would be another step for the Nationals, a team seemingly on the cusp of making a push, or fading, in the final month of the season.

Detwiler, who had lost his previous three starts not all because of his doing, was efficient and effective. The 25-year-old left-hander and sixth overall pick in the 2007 draft was brought up to the majors in July and brought into the rotation in early August because the Nationals believed in his potential and his arm.

Against the Diamondbacks, he made another good case to stay in the Nationals’ rotation beyond this season, following up his best start of the season five days prior. His sinker induced both groundballs (six) and sky-high flyouts (five). Detwiler scattered six hits and walked only one batter through 62 / 3 innings.

The only Diamondbacks hitter to give Detwiler, a former reliever as well, significant trouble was Henry Blanco, Arizona’s 39-year-old journeyman catcher and No. 8 hitter. In the third inning, Blanco easily handled Detwiler’s first pitch to him, a slider, knocking it for a single. In Blanco’s third at-bat, with two outs in the seventh, the catcher fouled off two Detwiler sinkers before smacking one into deep left field for a home run.

Washington's Jayson Werth watches his three-run home run off Arizona Diamondbacks pitcher Joe Saunders during the fourth inning. (Luis M. Alvarez/Associated Press)

“He was a little tentative but he recovered and pitched well,” Johnson said of Detwiler. “He’s got a great arm and when he’s real aggressive and he had a really good fastball and he was spotting it. He’s got a little sinker with it, too. I mean, that was impressive.”

After allowing an infield single to pinch-hitter Sean Burroughs, Detwiler exited the game to the rousing applause of the crowd. Henry Rodriguez and Ryan Mattheus combined to allow one base runner over the next 11 / 2 innings. Drew Storen pitched a scoreless ninth to earn his 34th save.

After the win, Johnson complimented Werth on his hitting, saying, “ ‘So you can hit left-handers.’ He was hitting like .165 against them.”

Werth’s deadpan response to reporters: “Yeah, I didn’t really appeciate that.” Then he offered a smile.