Kurt Suzuki has made an impact behind the plate, and at it as well. Of his game-winning hit Saturday, he said, “You definitely want to be in those situations. To tell you the truth, I was excited . . . You want to go up there and make them pay.” (John McDonnell/The Washington Post)

Trades that happen in August are supposed to be secondary, the kind that unload unwanted contracts, unwanted players or both. They can go unnoticed, and baseball just churns on.

On Aug. 3, three days after baseball’s non-waiver trade deadline, Washington Nationals General Manager Mike Rizzo sent a minor league catcher few Nationals fans had heard of, David Freitas, and shipped him to Oakland. In return, the Nationals got 28-year-old Kurt Suzuki. A blip of a deal? Their catching situation, their lineup, and in some ways their club haven’t been the same since.

Saturday night, Suzuki caught starter Jordan Zimmermann, helped reliever Ryan Mattheus work out of a jam, coaxed a bounce-back inning out of Tyler Clippard and hung in as Drew Storen gave up the tying run in the ninth. And in the 10th inning, when St. Louis Cardinals Manager Mike Matheny elected to walk the struggling Danny Espinosa to face Suzuki, he won the Nationals a game.

Suzuki’s low liner of a double to left-center scored the winning runs in the Nationals’ 6-4 victory, and was just the latest bit of his handiwork. Since taking over from the worn-down, beleaguered Jesus Flores as the Nationals’ every-day catcher, Suzuki has added to and served to emphasize the depth in Washington’s lineup. He might hit eighth, but in his 40 games with Washington, he now has 25 RBI.

“He added a pretty good spark,” Zimmermann said.

“That’s what he does,” Storen said.

What he has done is complete what is now a surprisingly potent Nationals’ lineup. Though he was hitting just .218 at the time of the trade, “I think we all knew his track record was better,” said third baseman Ryan Zimmerman. From 2009 to 2011, Suzuki hit at least 13 homers a year, and he once drove in 88 runs. Once he found his stroke in Washington, the Nationals became better.

“That’s a pretty long lineup to face,” Zimmerman said.

The situation Saturday night — with the Nationals inching closer to clinching the National League East — was as predictable as it was perplexing. Adam LaRoche opened the 10th by drawing a four-pitch walk off reliever Sam Freeman. After Roger Bernadina bunted LaRoche to second, Fernando Salas came on to relieve Freeman.

Salas got Ian Desmond to fly out. And then the strange strategy. Yes, Salas is a right-hander, and Espinsoa hits right-handed.

“I understand it,” Washington Manager Davey Johnson said.

But Espinosa has been flailing. He came into the at-bat 1 for his past 16. Suzuki was among the Nationals’ hottest hitters.

“You definitely want to be in those situations,” he said. “To tell you the truth, I was excited that they walked Espi. That kind of lights a fire under you. . . . You want to go up there and make them pay.”

So Suzuki did. His counterpart, Cardinals all-star Yadier Molina, helped matters when he allowed a passed ball, putting LaRoche at third and Espinosa at second. And then Suzuki unloaded on Salas, a line drive that hit the base of the wall in left-center. The tie was broken, and what might have been a devastating loss became a win.

“I really like his approach,” Johnson said. “He’s a gamer. He likes those situations. That was huge.”

So a throwaway August trade? Not at all.

“To have a good defensive catcher, it seems like they always know or have a sense of what the pitcher’s going to do to him,” Zimmerman said. “He’s been huge. That’s kind of an under-the-radar acquisition as far as compared to other teams and what they’ve got.”

Suzuki finished his night by watching college football and eating a postgame meal with some of the Nationals’ pitchers in the visitors clubhouse. He laughed with Stephen Strasburg and asked Gio Gonzalez about something. Mid-season trades can be jarring for players and teams alike. But here was Suzuki Saturday night, fitting into the lineup and the clubhouse, helping the Nationals win a game.

“I was really excited,” he said. “Coming to the best team in baseball, how can you complain?”