The 42-year-old Irabu was found at 4:25 p.m. PDT Wednesday, county sheriff's Sgt. Michael Arriaga said.
"He was found dead by an apparent suicide," Arriaga said Thursday.
Los Angeles County coroner's official Ed Winter said his office was not releasing any circumstances of the death other than it was being investigated as a suicide. The autopsy will be performed Friday or Saturday.
Neighbors described Irabu as a quiet, unassuming man who had apparently grown despondent recently because of a split with his wife.
Mary Feuerlicht said she was about to go pick up her son on Wednesday morning when a man came running down the driveway from Irabu's large two-story home, perched atop a hill with views of the harbor and downtown Los Angeles, pleading with her to call police.
Feuerlicht said she was later told by sheriff's deputies and the man who asked her for help that Irabu's wife had left him and took their two young daughters. She hadn't seen the wife or the kids for the past couple of months and didn't think anything of it because they regularly left town for the summer.
"When I saw him for the past month or so he seemed kind of down," she said. "He wasn't kind of perky like I've seen him before."
Former major league manager Bobby Valentine, now an ESPN broadcaster, managed Irabu in Japan in 1995. Valentine said he got the news Thursday when it came across on his mobile phone.
"I got a little sick to my stomach, actually," he said.
Irabu was billed as the Japanese version of Nolan Ryan when he arrived in the United States in 1997. But after an impressive major league debut with the Yankees that summer, he never came close to fulfilling such lofty expectations.
Rather, he always wore the label that late Yankees owner George Steinbrenner stuck on him after Irabu failed to cover first base during an exhibition game: "Fat ... toad."
"He was a world-class pitcher. When Nolan Ryan saw him he said he had never seen anything like it," Valentine said. "There were just some days when he was as good a pitcher as I had ever seen. A fabulous arm."
Irabu finished 34-35 with a 5.15 ERA in three seasons with the Yankees, two years in Montreal and a final season in the Texas bullpen in 2002. He was a member of two Yankees teams that won the World Series, but his only postseason action was a single relief appearance in the 1999 AL championship series when Boston tagged him for 13 hits.
Still, Irabu left a lasting legacy. Several big stars, from Ichiro Suzuki to Hideki Matsui, followed Hideo Nomo and Irabu from Japan to the United States.
"He was one of the pioneers," Valentine said. "There was a lot riding on his shoulders."
The right-hander made a comeback in April 2009 in the independent Golden Baseball League, going 5-3 with a 3.58 ERA for the Long Beach Armada. He then returned to Japan and was introduced that August as a member of the Kochi Fighting Dogs, saying, "I have high expectations for myself."
Irabu had his share of off-the-field trouble in recent years.
In August 2008, he was arrested in Japan for allegedly assaulting a bartender after drinking 20 mugs of beer. Police said he became angered after his credit card was rejected.
In May 2010, Irabu was arrested on suspicion of driving under the influence of alcohol in the Los Angeles suburb of Gardena. Police said he was stopped after his car drifted outside of traffic lanes and he nearly collided with a parked car.
He posted $5,000 bail but it was not immediately clear whether he was criminally charged.
"I think that he was one of his own worst enemies," Valentine said.
Irabu starred in Japan for nearly a decade before the San Diego Padres purchased his contract from the Chiba Lotte Marines. But Irabu declined to join the Padres, insisting he would only play for the Yankees.
The Yankees put together a package and traded for Irabu a few months later and signed him to a four-year, $12.8 million contract.
Irabu tuned up in the minors before making his big league debut at Yankee Stadium on July 10, 1997. The crowd was buzzing even before his first pitch, and fans on two continents watched him. T-shirts with "Typhoon Irabu" were on sale at the concession stands at Yankee Stadium and sushi was sold alongside the hot dogs and beers.
With current Yankees manager Joe Girardi as his catcher that night, Irabu retired the first six Detroit batters, striking out four of them and showing a 96 mph fastball. He fanned nine in 6 2-3 innings and got the win.
When he walked off the mound in the seventh inning, Yankees fans gave him a standing ovation. Some even bowed with both hands over their heads, and Irabu came out of the dugout for a curtain call.
That, however, was perhaps his finest moment in the majors.
"He was a work in progress. It just didn't progress I guess the way he had planned or the way some people planned," Valentine said. ---
Associated Press Writer Jacob Adelman contributed to this report
