Jayson Werth spent most of his first season in Washington a year ago hearing how the Nationals had overpaid for the free agent outfielder.

Not any more.

Werth delivered a walk-off home run Thursday that gave the Nats a 2-1 victory over the St. Louis Cardinals in Game 4 of the National League Division Series. He saved the Nats' postseason, at least for one night. It was the biggest home run in team history, eclipsing Ryan Zimmerman's walk-off homer in the first game at Nationals Park in 2007.

The fans didn't stop cheering for more than five minutes as Werth gleefully hurled his helmet skyward, jumped onto home plate and disappeared under a mob of teammates.

This was why the Nats were willing to pay Werth $126 million over seven years to come to a team that had lost 298 games over the previous three seasons. They needed someone used to winning and with postseason experience even if the team wasn't ready for it last season. Werth has a World Series ring from the Philadelphia Phillies, and his patience at the plate has helped his teammates, including Michael Morse. Indeed, Werth looked at a 2-2 pitch that seemed criminal not to foul off just before he hit his home run.

Werth has 14 homers in 48 postseason games, tied for ninth all time. By comparison, Yogi Berra hit 12 in 75 games, and David Ortiz has 12 in 66. Duke Snider homered 11 times, while Johnny Bench, Frank Robinson and Chase Utley hit 10 and Barry Bonds nine. So much for Werth being Werthless as a free agent signing.

Game 5 is Friday, with the winner advancing to the NL Championship Series, but it can't be any more dramatic than Werth's deciding swing.

Indeed, the game was the complete reverse of the one Wednesday, in which St. Louis clubbed Washington 8-0. The fans arrived energized instead of discouraged by a loss that left the Nats one defeat away from the offseason. The 44,392 cheered third strikes, razzed the umpires and stayed long after the home run. Indeed, they were chanting "Let's Go Nats" 10 minutes after Werth had won it.

Washington fans finally were rewarded with the team's first home playoff victory since the team arrived in 2005.

If the Nats don't win the series, it won't be because pitcher Stephen Strasburg was shut down last month. Washington possessed plenty of arms for its last chance. Ross Detwiler pitched six innings of two-hit ball. Jordan Zimmermann struck out the side in the seventh. Tyler Clippard did the same in the eighth, and Drew Storen whiffed the first two in the ninth before finishing with a fly ball.

But the Nats' batting malaise continued. They had only Adam LaRoche's homer and Zimmerman's single before Werth's homer. Werth hit two fly balls and struck out before dueling with Lance Lynn leading off the ninth. On the 13th pitch, he lined a fastball into the left-field stands.

It was all about one swing, and Werth's was worth $126 million.

"What a difference a day makes," he said. "I know we are going to come in ready to go [Friday]."

Examiner columnist Rick Snider has covered local sports since 1978. Read more on Twitter @Snide_Remarks or email rsnider@washingtonexaminer.com.