The Red Sox were jogging off the field after a 1-2-3 sixth inning on Opening Day in New York when Mike Napoli shouted frantically at Dustin Pedroia.

“Watch this! Watch this!” Napoli said. “Get in the dugout! You’ve got to see this!”

Ryan Dempster had already similarly alerted Clay Buchholz.

“You’ll want to watch this,” Dempster said, without spoiling the surprise.

What happened next was unlike anything anyone in a Red Sox uniform can recall seeing at any level. Koji Uehara didn’t just enter the dugout. The reliever assaulted it.

Unleashing what Jacoby Ellsbury calls, “his war cry,” Uehara ran the high-five gauntlet, alternating between hitting teammates with his bare hand and glove.

“I got there at the end,” Pedroia said. “Whoa. Take it easy. You’re going to break my hand.”

Ten games into a season that has the Red Sox playing .600 baseball after yesterday’s 2-1 win against the Tampa Bay Rays in 10 innings at Fenway Park, one of the most pleasant — and loudest — surprises has been the work of Uehara, a 38-year-old right-hander with a floppy Beatles haircut and the playful temperament to dispel nearly every stereotype in the book about buttoned-down Japanese players.

Yesterday brought some of his best work yet. Called upon in the ninth inning of a 1-1 game after closer Joel Hanrahan walked the first two batters, Uehara struck out James Loney and retired Yunel Escobar and Ryan Roberts on pop-ups.

And then Uehara basically lost his mind, transforming into one of Hayao Miyazaki’s creations from “Princess Mononoke” or “Spirited Away,” unleashing the celebration that is quickly becoming his trademark.

“I just try to stay tense, because if I’m loose when I give him a high five, my arm is going to dislocate,” Will Middlebrooks said jokingly. “He goes back and forth between hand and glove. I try to get a glove. Glove is better for me. There’s hands and spit and Japanese slang flying everywhere. He’s really a calm and funny person, but whenever he has a clean inning, he goes berserk. And I love it.”

The Red Sox front office had no idea this was part of the Uehara package when he signed as a free agent in the offseason. No one knew except former Texas Rangers teammates Dempster and Napoli.

“When he gets out of tough situations, he’s even a little more animated,” Napoli said. “In Toronto his interpreter tried to give him a cup of water, and he just spiked it, and water’s flying everywhere and Jonny (Gomes) is all fired up. He throws in a, ‘Hie!’ or something Japanese. He just goes off. It’s good, man. It’s good for the team.”

There’s some dispute over what exactly Uehara screams. Napoli hears Japanese. Daniel Nava has heard, “Let’s go!” Buchholz hears a mish-mash.

“It’s yelling and screaming,” Nava said. “Most of the team is laughing. He’s a really funny guy. It’s just his mannerisms. And the English that he does know, it’s how he says it. You know how there are just people in your life that the way they go about things, they’re funny? He’s one of those guys.”

Uehara may be a character, and he may be playing to his audience just a bit as his celebrations grow increasingly delirious — “I’m always icing my wrist,” Uehara deadpanned — but Dempster wants his teammates to understand one thing.

“Just know that it’s real,” Dempster said. “We frown upon enthusiasm in the big leagues. We can’t have a guy make a good play and then smile. That’s not the way to do it. Koji likes to live on the edge and we appreciate it. It’s awesome.”

Unlike Ichiro or Yu Darvish, Uehara has not drawn a huge following of Japanese media; just three reporters watched him yesterday. Daisuke Matsuzaka still draws more Japanese media in Triple A with the Cleveland Indians, which those close to Uehara say rankles him.

At the rate he’s going now, Uehara won’t be worrying about it much longer, because we may just be looking at the birth of a folk hero.