Player representatives around the Majors were some of the first to find out about the news and also had some of the strongest opinions on Fehr and the change.
D-backs first baseman Tony Clark, who is an associate player representative on the MLBPA Executive Board, had especially kind words to say about Fehr.
"The impact that Don has had on me as a player and on me as an individual is immeasurable," Clark said. "What he has done over the course of the last 25 years, it's going to be very difficult to truly appreciate. All that he stood for and all that he has fought for inevitably at the end of day was always in our best interests. It's not a coincidence that our union has grown and strengthened over the course of his tenure."
Cubs pitcher and player representative Ted Lilly had nothing but positive things to say about Fehr and was even a little sad that Fehr was stepping down.
"In some ways it's disappointing for the union," Lilly said. "He's done an incredible job. Clearly. You understand his position. He's worked his tail off for a long, long time. He's given it everything he had. I think he'll probably still be around to some degree."
Fellow player representative Jeff Francoeur was also proud of Fehr for agreeing to drug testing in 2002 to help clean the game of performance-enhancing drugs.
"I think he's done a great job the last four or five years of getting stronger 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.
Players appreciate Fehr's role in rising salaries for players, as the average salary in 1983, when Fehr began his tenure, was $289,000. It stands at $3.3 million this year.
"We are set up for the future," said Marlins veteran Wes Helms, an assistant player representative. "We think of the way life is, and we've built a foundation where we've basically been taken care of, whether we are free agents, or arbitration guys, and so forth. 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. We owe a lot of that to him."
But Fehr didn't do it without some controversy, as he had three work stoppages on his watch, including a 7 1/2-month strike in 1994-95 that wiped out the World Series for the first time in 90 years.
Players, however, saw the good that came out of the strike and that there has been labor peace since then, with the current Collective Bargaining Agreement running through the 2011 season.
"I think the obvious thing is that he helped the players to be unified over the years and through multiple bargaining agreements," said the Orioles' Jeremy Guthrie, who sat on a 10-player sub-committee dealing with the change over the past few weeks. "Unfortunately, the players went to strike in 1994, but he felt it was important for the players' rights. In a sense, the agreement from 2002 has always put the players and the game first, and the players have been treated fairly and the game has continued to grow.
Big leaguers such as the Blue Jays' Vernon Wells, also a player representative, felt that Fehr left the union in great shape, with Michael Weiner expected to take over as union head.
"It's been a long and great run with him representing the teams," Wells said. "At the same time, it's one person stepping down and eventually someone stepping in who's going to be able to take his place rather nicely and the union is going to be as strong as ever."
Former players also had plenty to say about Fehr.
"He's had a huge impact on the players," former Astros player Craig Biggio said. "When you get into these negotiations between ownership and the players, you need someone to represent you. He's done a great job as far as when you're in tough times and a tough situation and you look at what the amount of revenue made in baseball up until the slide this year, he's done a tremendous job by the players. We've been lucky to have him."
Andy Fox, who played from 1996-2003 and now is a coach with the Marlins, thinks Fehr played a large role in baseball seeing record revenues over the past few years.
"The game of baseball changed from the players' standpoint," Fox said. "He worked under Marvin Miller, I believe, and he kind of took on his vision of a union. Now, it's turned into probably one of the bigger unions in the world. The game has gotten bigger each decade. You can see that the way salaries have grown. I think Donald saw that. No player can ever complain about how the system is now, because they all benefited from it."
Perhaps former All-Star first baseman and current FOX broadcaster Mark Grace had the kindest words for Fehr.
"I got to know him very well over the years," Grace said. "He is the smartest guy I've ever met. He did a boatload for us. His guy and his mentor was the great Marvin Miller. He's been an extension of Marvin Miller, and Don wanted to be known as an extension of Marvin Miller. Not only myself, but every, and I mean every, ballplayer should dropp down on our knees and thank the Good Lord that he put Don Fehr as the head of the player's union."
Here's what some other current and former players had to say about Fehr:
Dodgers infielder and associate player representative Mark Loretta:
"Don's the smartest guy I've ever been around. Very analytical. His recall is incredible. A bright guy. He didn't make decisions rashly or without a lot of thought. I hope he gets into the Hall of Fame. He deserves it, as does Marvin Miller."
A's reliever and player representative Brad Ziegler:
"Unfortunately, in today's media market, he's probably going to be remembered more than anything for the steroids stuff and drug testing, and the  strike. But if you look at his body of work, he's done so much more than that -- so much positive stuff. To me, avoiding a strike in 2003 was probably the biggest positive. 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, so be able to move on past that."
Rangers reliever and player representative C.J. Wilson:
"I just thought he was extremely even-keeled. When you're dealing with unions and owners and there are billions of dollars on the table, you have to have someone who is level-headed and is not going to rush into any decisions. He did everything in an orderly fashion. I always felt he was a guy who dotted every "I" and crossed every "T" before getting things done. He was always on top of every detail."
Giants veteran Rich Aurilia:
"I think a lot of us who have been either player reps or on the board have probably known for a few years that Don was ready to step down. I think he as much as possible wanted to see the drug policy through, get as close to the next bargaining agreement as he possibly could. I'm happy for him that he gets to step away and enjoy his own personal life instead of worrying about a thousand other guys, running around the country."
Angels outfielder and player representative Gary Matthews Jr.:
"During his time, it's become a broader, more international [union]. I think the secret to his success was his ability to reach players from different eras. With players from the '80s, there was a lot more friction between the players and owners. Not to say there aren't disagreements now, but his ability to communicate with players from different cultures, different socioeconomic backgrounds. His ability to navigate his way through so many situations has been impressive. Donald Fehr was able to make adjustments with players from era to era, to stay on top of things for a long time. He's been a tremendous leader for us."
Former Major League pitcher Frank Tanana, who played from 1973-93:
"I felt he always kept the players well informed, and I was always proud of his ability to keep the players definitely united, kind of dealing as one. We had complete confidence in him as our head, and I think he did a great job."
Former Major League third baseman Matt Williams, who played from 1987-2003:
"He was one of the big reasons that the Players Association continues to be strong and continues to be a well-run and united organization. He's done a lot of things for the players. He got a lot of help for alumni, guys no longer in the game and didn't make the same amount of money that my generation or this generation made. He worked with Major League Baseball to help them."
Former Major League pitcher Orel Hersisher, who played from 1983-2000:
"I thought he worked very hard for us. 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.
You're always not going to be liked by everybody when you're in a position of leadership, simply because there are always going to be certain people who don't like you. But he was very good at not turning them away. He was good at listening to them and being sensitive to their opinions."
Current Giants broadcaster and former Major League pitcher Mike Krukow, who played from 1976-89:
"The things that he's done for us are amazing, and the heat that he's taken has been absolutely right in the middle with every controversy, from free agents to steroids. He definitely had a lot of turmoil during his tenure. I'm going to miss him. He was really good at what he did. That's not an easy job to do.
We really realized what they did in 1981 when we went through the strike and got a little window into their lives. They do a great job.
He's not ever going to get praise, because of his relationship with the media. He was always on the opposite side, and he took shots for so long. He should be applauded for his effort."
Rhett Bollinger is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.