Baseball people say he's bright, opinionated and hot-tempered. They say he's competitive enough that he fired one general manager after he'd owned the team only 17 months and another five years after that.
He gave million dollar contracts to free-agent pitchers Nolan Ryan and Don Sutton and even paid $450,000 for utility infielder Dave Roberts.
They say, too, that he's a very independent thinker, and that if he wants to move the Astros from Houston to Washington, he will do it.
As John J. McMullen makes headlines here this week, a lot of people in and out of baseball are wondering about this 67-year-old naval architect, who he is and what his intentions are.
Many people know his actions, but not many know the man.
"The great danger in life is to go stale," he told a reporter in 1979, just after buying the team. "I've got to be moving, doing things."
After watching his first game in the Astrodome, in 1980, he told a reporter: "There is no stadium in the world to compare with this. I can imagine what the enthusiasm will be like when the place is filled. And we intend to fill it."
An American League general manager said of McMullen: "There have been National League owners' meetings where 11 of 12 guys are in absolute agreement. But if John is the guy who disagrees, no one is going to change his mind, and he's going to try to change everyone else's mind."
His biography in the Astros' media guide has called him "one of the new breed of sports owners." He owns the New Jersey Devils of the National Hockey League and is a former minority owner of the New York Yankees.
A 1940 graduate of the U.S. Naval Academy, he lives on an estate in Montclair, N.J., has offices in Manhattan and Arlington, Va. He is chairman of John J. McMullen Association, Inc., a naval architecture firm, owns about a dozen other companies and numerous real-estate holdings.
When he bought the Astros, he emphasized he was a businessman, not a baseball man. But for an owner who said he would stay in the background, McMullen was very much in baseball's foreground, very quickly.
In the hours after the Astros lost the 1980 National League playoffs to the Philadelphia Phillies, McMullen was heard telling friends at a cocktail party how his manager, Bill Virdon, had been outmanaged.
Two weeks later, he fired Tal Smith, the Astros' popular and respected general manager and architect of that championship team.
The spring before -- 10 months after he bought the team -- he was in a public debate with Smith over several baseball decisions. (He wanted to sign free-agent pitcher Nolan Ryan for $1 million a year, but didn't think much of signing J.R. Richard, then the best pitcher in the National League, for half that much.)
Nine months after their disagreements became public, McMullen fired Smith, a move that caused National League president Chub Feeney to say: "It's one of the worst things I've heard of in baseball."
It was such a stunning move that McMullen's partners tried to oust him as managing general partner.
He hired an old buddy, Al Rosen, to replace Smith; then fired Rosen after the 1985 season to bring in former Cincinnati Reds General Manager Dick Wagner.
"John makes comments around some general managers and other baseball people and can stop a conversation for five minutes," a former minority owner of the Astros said. "He has everybody looking into their soup."
He was once a regular at Astros' home games, now he seldom shows up. When press reports surfaced about the Astros possibily moving to Washington, McMullen stepped up his criticism of a city he says doesn't support his team.
The criticism of him in Houston is sharper than ever, with one former employe saying: "He thinks he markets that team? That's crazy. He's looking for an excuse."
"It's absolutely ludicrous," said Gene Elston, the Astros' radio voice for 25 years. "This is too dynamic a town and too great a population area to lose its baseball team."
McMullen turns 68 this year, and it was supposed to be one of the Astros' grandest seasons. Smith had gotten Harris County to push through a $43 million renovation project on the Astrodome and its surroundings, and, as part of Texas' sesquicentennial celebration, Houston will host the 57th All-Star Game.
But sometime since the day in 1979 when McMullen called the Astros "the best young team in baseball" and promised to bring Houston a World Series "in two to three years," things have gone sour.