Gio Gonzalez struck out 10 Pirates in the win. (John McDonnell/The Washington Post)

The last man on the field was Adam LaRoche. Every other player jogged to the dugout between the seventh and eighth innings Wednesday night. LaRoche, having just delivered the most crucial hit in the Washington Nationals7-4 victory over the Pittsburgh Pirates, ambled from second base to his position at first. The Nationals Park crowd recognized the opportunity.

The 25,942 stood and showered him with an ovation. LaRoche offered a small grin — that’s all he’s got in the grin department — and tipped his cap. How many in that crowd hoped for Prince Fielder this winter? How many believed LaRoche would be the Nationals’ most indispensable hitter? And what, in any event, does any of that matter now?

Injured all of his first season in Washington, LaRoche this year has been the lone offensive constant for a first-place team flooded with injuries. Wednesday night, LaRoche drilled his team-best seventh homer in the sixth inning and then, in the seventh, smoked a first-pitch, bases-loaded, line-drive double to right that scored three more runs. The second drive turned a one-run game into a comfortable victory — even after a three-batter save by Henry Rodriguez — and let Gio Gonzalez earn his fifth win of the season.

“It was really special, to say the least,” LaRoche said. “Obviously, going through what I did last year and not being able to be a big part of it, and now to come back and have [the fans] behind me the way they are, it was perfect.”

LaRoche went 3 for 4, his latest stuffed box score in a season full of them, enough even to overshadow Bryce Harper’s first career triple in the first inning. Last year, LaRoche hit .172 for 43 ineffective games with a tear in his labrum before he finally succumbed to season-ending surgery.

This season he has not only returned but, at 32, is having a career year. While playing above-average defense, LaRoche is hitting .339 with a .595 slugging percentage and 29 RBI. His 1.024 on-base plus slugging percentage ranks eighth in the majors. He is on pace to make his first all-star team. The game will be played in Kansas City, “right up the road from our ranch in Kansas,” he said.

Not that it ultimately matters, but this fact may bring another small grin to LaRoche’s face: Fielder, whom the Nationals flirted with before he signed with the Detroit Tigers, has underperformed him in every significant offensive category.

“He’s making that move look real good — that lack of move,” Manager Davey Johnson said of LaRoche. “He’s only human. ‘I want to show everybody, what were you thinking about, with the Prince?’ ”

Except LaRoche, the son of a big leaguer, betrays no such sentiment. His teammates revere him for his even-keeled personality.

“I don’t think he was upset about it, trying to prove anything to anyone,” said shortstop Ian Desmond, who hit a solo homer. “He probably was well-rested and had a good hunting season.”

LaRoche paid little attention to the Fielder rumors. He did not feel like he needed to validate his two-year, $16 million contract. But he did have something to prove.

“To myself, I did,” LaRoche said. “I don’t look at what’s going on on the outside and feel like I’ve got to come here and prove the salary or prove missing a year last year, whatever it is. But as a competitor, I wanted to prove to myself that I could come back from this surgery and do what I know I’m capable of doing.”

The big-ticket acquisition the Nationals did make, Gonzalez, delivered again Wednesday. He struck out 10 in seven innings to overtake rotation mate Stephen Strasburg for the National League lead with 60. He allowed three runs on four hits and two walks, and for almost the entire night was utterly dominant.

Rodriguez entered in the ninth inning, having imploded in three of his past five appearances. Johnson promised he would use Rodriguez in a save situation, and he did — even if Ryan Mattheus warmed up behind him to start the inning. Rodriguez made it look easy — an error by Desmond, a strikeout and a 6-4-3 double play.

“We believe in Henry 100 percent,” Gonzalez said. “The only one who can hurt Henry is himself.”

The Pirates couldn’t do much against Gonzalez, either. The first seven Pirates hitters swung and missed nine times in 29 pitches. He retired 10 in a row at one point. After Gonzalez got the first out of the seventh with one pitch, with the Nationals up 4-1 after LaRoche and Xavier Nady had drilled back-to-back homers — giving Nady 100 for his career — he seemed on the verge of cruising to the finish of another dominant start.

Even after Gonzalez issued his second walk of the game, it seemed harmless, especially after the second out. Then Josh Harrison drilled a 2-1 fastball to the left field seats. The home run was the first Gonzalez had allowed in 58 innings going back to last season.

Then LaRoche came through. Pirates reliever Evan Meek walked Harper and Ryan Zimmerman to load the bases for LaRoche, which this season means disaster. He fired LaRoche a first-pitch, 95-mph fastball. LaRoche let fly his fluid swing: all wrists, the kind of easy movement you make trying not to wake a baby while shutting the car door.

The ball screamed into the right field corner. The bases emptied. LaRoche stood on second base as the park erupted. Many in the crowd, this winter, had not wanted LaRoche. Now, they could not imagine this team without him.

On the scoreboard, the Nationals congratulated LaRoche on his 1,000th career hit. He would later give the ball to his father. LaRoche thought about all the teammates he had played with. He flashed back in his mind to his very first hit, in 2004, and all the memorable hits since. Few had felt as good as this one.

“Oh, man, it’s pretty special,” LaRoche repeated. “Just a perfect night.”