Nationals right fielder Jayson Werth is the only hitter among the NL’s top five in batting average (.320), on-base percentage (.396) and slugging (.523). (John McDonnell/The Washington Post)

In August of last year, Jayson Werth had doubts. He could not hit balls over the fence in batting practice. Surgery had left him with plates and screws holding his left wrist in place. He could still launch an occasional home run in a game, when his bat met the ball in the right spot at the right time — “accidents,” he said. In BP, he lacked the raw power he had felt in his swing his whole life. “You wonder if it’s ever going to be the same,” Werth said.

In the spring, he started hitting batting practice fastballs out of Space Coast Stadium. The doubt disappeared for him, and now, months later, it has for everyone else. Written off after a bleak first season as a Washington National and diminished after a broken wrist in his second, Werth has bashed his way to the top of National League leader boards and the fringes of the most valuable player discussion.

The standard criticisms of Werth — too old, overpaid, never carried a team in Philly, anyway — have faded as he has been one of the NL’s best hitters since the all-star break. “I think he’s a better hitter than he was here,” Manager Davey Johnson said Wednesday afternoon at Philadelphia’s Citizens Bank Park.

In the second half, among hitters with enough at-bats to qualify, only Mike Trout and Miguel Cabrera have a higher OPS. Over the full season, Werth is the only hitter among the NL’s top five in average (.320), on-base percentage (.396) and slugging (.523). In 2010, the season most responsible for Werth’s seven-year, $126 million contract, he hit .296/.388/.532.

“I feel like I’ve evolved,” Werth said. “I got through another career-threatening wrist injury. At the same time, I feel like I’ve always been this type of player and capable of putting up these type of numbers. I’ve always thought that, regardless of what the stat sheet says or what the people in the paper write or what the guys on TV say or what the umpires call.”

The Post Sports Live crew discusses the Nationals' slim chances of making the playoffs and whether it matters that Bryce Harper hid his hip injury from Manager Davey Johnson. (Post Sports Live/The Washington Post)

Werth says his revival should have happened last year. On May 5, 2012, he belted a home run that nearly landed on the left field concourse at Nationals Park. “It was off [Vance] Worley,” Werth said. “Front-hip cutter.” He was starting to feel locked in, his power coming.

The next night, he slid to catch a sinking line drive in right field. His glove caught on the turf, and he knew immediately he had broken his wrist. He missed the next three months.

Werth didn’t play at all in 2006 after he finally found a surgeon who could repair a rare kind of ligament tear in his left wrist. With another injury, he wondered again.

“Until you really get some kind of substantial contract that keeps you in one place for a long time, there’s always doubts,” Werth said. “This game is not easy. There’s always somebody right behind you to take your place.”

A swing adjustment

Werth began this season at a pedestrian rate. He batted .260/.308/.400 through May 2, at which point he landed on the disabled list and missed a month with a strained hamstring. In mid-June, nine games after he returned, his average bottomed out at .244.

At about that time, he watched Bryce Harper swing in the batting cage. Harper held his hands high, away from his body. Werth pored through old footage and realized, yes, he once started his hands in a similar place — level with his ear rather than armpit level. He made the switch.

“You always want to have your hands come up to come down through the ball,” Johnson said. “When he was starting them low, he would bring them up. But sometimes he wasn’t comfortable with the position he’d get into when he was bringing them back up. Now he’s starting closer to the area where he’s going to pull the trigger, and he’s really confident his timing is going to be better.”

Since July 1, Werth has hit .365/.450/.600 and invited comparisons to his time in Philadelphia. “He seems like pretty much the same player he was here,” Phillies second baseman Chase Utley said. At 34, he may actually be changing, even improving.

Always patient and selective, Werth has worked more aggression into his approach: He has seen fewer pitches per plate appearance than any season of his career, but he has still tied for the NL lead. Phillies catcher Carlos Ruiz has seen him hit more balls to the right-center field gap.

“I think he’s more refined as a hitter,” Nationals outfielder Scott Hairston said. “I’ve seen him go 0-2 to 3-2, foul a couple pitches off, and take a nasty slider — shin-high, outside — and shoot it to right field. That’s very difficult, especially for a power hitter like him. He’ll change throughout the at-bat. If it’s a 2-0 count, he takes a big rip. If it’s a 1-2 count, he’ll stay within himself.”

The eight nights of Bale

One night in July, Werth watched “American Psycho,” in which Christian Bale plays a deranged Wall Street executive. The next day, Werth blasted two home runs against Clayton Kershaw. He watched another movie starring Bale the next night. He crushed two more homers the next day.

“It was like eight straight nights of Christian Bale,” Werth said.

On the eighth night, Werth watched “The Machinist.” In that one, Bale plays an industrial worker whose insomnia leads to insanity and emaciation. Werth walked into the clubhouse and saw first baseman Adam LaRoche. “Rochie,” Werth told him, “I watched a movie about you last night.”

“I took an 0-for,” Werth said. “And that was the last time I watched a Christian Bale movie.”

Baseball draws a thin line between superstition and routine. Werth has brushed aside most questions about his scorching streak. After one game, he shared the change in his hand positioning. Later, he offered his revelation about watching Harper to a Yahoo Sports reporter. Mostly, he has kept quiet about his success.

“Sometimes, you can get caught up in psychologically thinking yourself out of streaks,” Hairston said.

The grandson of a 19-year major leaguer and nephew of a 13-year veteran, Werth embraces baseball’s mental grind. He feels better when he hits well, of course, but he focuses more on the competition. “I always have fun coming to the park,” Werth said. “I’ll have fun coming to the park until they rip the jersey off my back, performing or not performing.”

Said LaRoche: “He’s the same different he’s always been.”

‘More is more’

After Werth signed with the Nationals in December 2010, he bought a plot of land and a house in suburban Virginia. After the 2011 season, when he hit .232, the construction manager on his renovation told him, “More is more.”

They were talking about the perils of adding on to a home, but it resonated with Werth on a deeper level. The contract he signed had solved one set of doubts, but it suffused him with a set of new ones.

“It’s a vicious cycle,” Werth said with a laugh. “It definitely doesn’t make it easier. It comes with more responsibility, more pressure, more — just more of everything.”

By last season, Werth had relaxed. He knew his teammates, coaches, trainers. They all knew him, his sense of humor, his high standards.

“He wants to be great,” former teammate Cole Hamels said. “In order to be great, though, I don’t think you can put a whole weight on your shoulders. You have to slowly progress. I think that’s what he realizes. He wanted it so quickly, as opposed to just letting it take off.”

Werth’s rebound inspires optimism for the remainder of his contract. He will be 38 at the end. Baseball’s standard aging curve suggests he will be greatly diminished. But it also suggested regression this season. Age always wins, but some players delay defeat longer than most.

“I am a late bloomer,” Werth said. “I feel like this last couple years, I’m finally getting to be where I can put on weight and keep it on. I’ve always been real skinny. I feel like that’s just who I am, anyway, regardless of the time missed. That’s why I feel like I can play this game for a long time.”

Wednesday evening, after he finished batting practice, Werth walked along the edge of the visitors’ dugout at Citizens Bank Park and signed autographs. He reached above the top of the dugout and grabbed an old baseball card. In the picture he had no facial hair, and his Phillies jersey hung off him.

“Doubt,” Werth said a few moments later, “has kind of withered away.”

James Wagner contributed to this report.