One thing he has never done is waver an inch from his powerful post as head of an ironclad union.
That changed dramatically Monday when Fehr, 60, announced that he will leave his position by the end of March.
On a conference call, Fehr told player representatives from the 30 Major League clubs that he was exercising a nine-month notification clause in his contract and would be replaced by union general counsel Michael Weiner pending approval of the union's executive board and then an advisory vote of the rest of the players.
"It has been a high privilege to be entrusted with the leadership of this extraordinary union for the last 25 years, and I am enormously proud of what the players have accomplished during that time," Fehr said in a statement.
"But now, about two years before the next round of collective bargaining, is the right time for me to relinquish my position and for the players to name new leadership. Accordingly, I have informed members of the executive board that I will resign effective no later than next March 31."
Fehr leaves behind a career of conviction and steadfast devotion to the players based in large part on the legacy and values of his pioneering predecessor, Marvin Miller. Fehr also will forever be remembered for the controversial stands he took against the league in various disputes over the years.
Fehr served through three work stoppages: a two-day midseason strike in 1985, a 32-day Spring Training lockout in 1990, and the 1994-95 strike that wiped out the '94 postseason and delayed and shortened the '95 season.
But baseball lovers who suffered through those impasses have enjoyed the fruits of the labor peace that has since prevailed, as has Commissioner Bud Selig, who has run the sport since taking over in an interim role in September 1992.
"For more than 25 years, Don has represented his constituency with passion, loyalty and great diligence," Selig said. "Although we have had our differences, I have always respected his role.
"In recent years, we have worked together to find common ground for the betterment of the game, which will have resulted in 16 years of unprecedented labor peace by the end of our current collective bargaining agreement. We hope to continue to build upon the game's prosperity as we work with the new leadership of the Players Association. On behalf of Major League Baseball, I wish Don great health and success in the future."
Throughout baseball, players were effusive in their praise of Fehr's lasting contributions to their union.
Marlins veteran and assistant player representative Wes Helms said Fehr's tireless service has ensured that the well-being of the Major League player will continue to be a priority.
"We are set up for the future," Helms said. "We've built a foundation where we've basically been taken care of. Don has been a great contributor to that. He's done exceptionally well. I think all the players in the game today owe him a lot. We've been taken care of very well."
Fehr's 25-year ride began when he succeeded Kenneth Moffett as acting executive director in December 1983 and was formally elected two years later. Moffett succeeded longtime executive director Miller in 1982.
Under Fehr's leadership, the average salary for players rose from $289,000 in 1983 to more than $3.3 million this season, the union said. When Miller took over in 1966, the average yearly salary was $19,000.
And when labor disputes made it to the nightly news before home runs or web gems, Fehr had no fear.
He stoically and methodically took the heat for the union as it battled the league.
"I thought he worked very hard for us," said former Major League pitcher and broadcaster Orel Hershiser. "I thought he was a good listener. As skilled as he was as a negotiator, his real skill was keeping things together and not panicking when things got tough."
"Unfairly, people look at him negatively," added San Francisco Giants outfielder and player rep Randy Winn. "Whenever he's on TV, he's talking about a possible work stoppage or the bargaining agreement. But I think he's a fan of baseball and has done a lot for the game."
Former big-league reliever Norm Charlton said he thought the public often got the wrong impression of Fehr.
"There were times he couldn't say what he wanted to say," Charlton said. "I think he was a brilliant man. ... He had to bite his tongue and not say things when he wanted to, but he was a great leader for our union and will be missed dearly."
Oakland A's reliever and player rep Brad Ziegler agreed, saying Fehr rose above the negativity and came through with one signature moment.
"To me, avoiding a strike in  was probably the biggest positive," Ziegler said. "That went right down to the wire, and he knew that after all the game had done to get fans back, a strike at that point might have been something the game wouldn't have recovered from. That was huge for the game, to be able to move on past that."
Now the game moves on without Fehr, but the man who will replace him brings plenty of experience to the position. Fehr's tenure could more than likely close at the end of the year with Weiner taking over if the voting process among the players runs smoothly as anticipated. The nine-month window was originally written into the contract to give the PA time to do a search for an executive director or to go through the selection process they are embarking on now, which will probably take a lot less than nine months because the union has a hand-picked successor.
Weiner, a 1986 graduate of Harvard Law School, has been with the Players Association since 1988. He has been the staff counsel, with the primary responsibility for administering and enforcing the Basic Agreement, for more than 10 years. Named general counsel in 2004, he has been in charge of all legal matters involving the Players Association.
Along with the union's chief operating officer, Gene Orza, and Steve Fehr, Don's brother, Weiner has formed the backbone of the MLBPA for years. In a matter of weeks, the union's executive subcommittee should recommend Weiner to the full board. If the board approves, Weiner's name will then be submitted to the players at large, who will have the remainder of the season to vote.
Weiner said he doesn't want to get too far ahead of the process at this point.
"My take is that it's a very humbling experience for me to even be considered," Weiner said. "We had a staff meeting today and Don and Marvin were there. Even to be possibly considered in the same sentence with them, for a labor lawyer, a labor official in this country is again pretty humbling.
"There's not much more I can say because this is all subject to player votes and membership votes. But I thank Don for everything he's imparted to me and the trust he's placed in me over the years. I think the focus now should be on his truly remarkable tenure."
If the voting process should end early, Weiner said, Fehr could step down well before the March 31 departure date. With no sense of a rocky road ahead, Fehr made it clear that Weiner is the one.
"Michael has been at my side during all the battles we have fought over the last 20 years and has been a major part of our successes," Fehr said. "He is clearly the most qualified person to become the next executive director and carry on the work of the Players Association in the years to come."
Fehr wasn't the only one with that opinion.
Dodgers infielder Mark Loretta, who ranks higher than regular player reps as an Associate Player Representative on the MLBPA Executive Board, called Weiner "the perfect guy to step in."
"He's been there for 20 years," Loretta said. "He really knows the ins and outs of the Collective Bargaining Agreement. He might be even more intellectual than Don. Don was good in front of the cameras and on Capitol Hill, and Michael isn't into that. But he's as sharp and prepared. He wears Converse, those Chuck Taylors. I've been nothing but impressed."
Now Weiner has some even bigger shoes to fill, with his departing boss having done this since August 1977, when Fehr joined the Players Association under Miller's tutelage as general counsel.
Two years prior, while working for the Kansas City law firm of Jolley, Moran, Walsh, Hager & Gordon on behalf of the union, Fehr was on the plaintiff's side in the landmark case involving pitchers Andy Messersmith and Dave McNally, which overturned the reserve clause and opened the door to free agency.
Fehr also negotiated a $280 million settlement in 1990 of free agency collusion cases involving the 1985-87 offseasons.
In recent years Fehr has also had health issues. In 2004, Fehr had his gall bladder removed, but two weeks later testified at a U.S. Senate Commerce Committee hearing on Capitol Hill.
"Overall I think he's done a really good job," said Miller, who served as the union's executive director from 1966-82 and fought many of its early battles. "He's at the point where he'll be leaving next year and there's every indication that he's leaving a union that is solidly unified. He's faced some very difficult circumstances, problems to deal with."
Cardinals manager Tony La Russa said having Miller as a mentor left Fehr with one very clear objective.
"Whatever was best for the players," La Russa said. "The priority is not the ownership and it's not the game. It's making the membership happy. ... It will be interesting. I heard that Fehr has said that mistakes were made during the steroid time. I'm glad he said that. It's true."
To that end, under increasing pressure from both houses of the U.S. Congress and ultimately from many of the players themselves, the 2002 Basic Agreement included a landmark Joint Drug Agreement, under which testing for performance-enhancing drugs began. The agreement has been amended three times since, most recently in 2008, to include more frequent and random testing and more stringent penalties.
"He said he felt he needed to be there to help the game of baseball through that tough time, but now he feels that the issue has been well addressed," said pitcher Jeremy Guthrie, the Orioles' alternate player representative, who was part of a 10-player subcommittee that worked on the changeover during the past month.
"I think he thinks, moving forward, that this was his best time. His family is in the forefront of his thoughts, wanting to spend more time with them. And that's an admirable thing."
Atlanta Braves outfielder and player rep Jeff Francoeur echoed that sentiment, saying Fehr helped make the MLBPA "the strongest union in professional sports."
"I also think he's done a great job the last four or five years of getting stronger [drug] testing in place," Francoeur said. "Guys are getting pegged now. That's not necessarily good for the image of the game. But it's good for the integrity and future of the game."