In a move that was a surprise in its timing, Wakamatsu was dismissed as Seattle's manager by general manager Jack Zduriencik and replaced on an interim basis by Daren Brown, the organization's Triple-A manager for the past four seasons.
Also dismissed on Monday were bench coach Ty Van Burkleo, pitching coach Rick Adair and performance coach Steve Hecht. Roger Hansen, the Minor League catching coordinator, was named as the new bench coach, and Carl Willis, in his first season with the organization as Minor League pitching coordinator, becomes the new pitching coach. Pedro Grifol also becomes part of the revamped staff.
"I do not take this decision lightly. I have wrestled with this," Zduriencik said at an afternoon news conference at Safeco Field. "I have thought through it long and hard. However, at the end of the day, a decision had to be made. And my decision, my recommendation, was that we make a change at the top of our on-field personnel. We did that today.
"I realize that our fans would like for me to go into great detail on how I arrived at this decision. The truth of the matter is, I had lost confidence in Don, Ty and Rick as the best fit for us this season and as we move forward.
"New leadership is needed and it is needed now. I expect Daren, Roger and Carl to provide that leadership, both in the clubhouse and on the field."
The shakeup comes less than one year after Wakamatsu guided the Mariners to a 25-game improvement.
Wakamatsu did not attend Monday's news conference but later issued a statement released by the team.
"I would like to thank the city of Seattle and all the baseball fans here in the Northwest for the great support offered to me during my time as Mariners manager," Wakamatsu said. "My single biggest disappointment is that we were not able to finish what we wanted to finish here, bringing a championship club to the fans. I can not tell you how great the fans were to me, and to my family. The support I received here will always mean a great deal to me."
"This has been an emotional day for Don, Ty and Rick, as well as myself," Zduriencik said. "They are all good people. I have great respect for them as individuals. I have great respect for their families."
Wakamatsu piloted the Mariners to an 85-77 record and third-place finish in the American League West last season, which helped remove the sour taste left over from the 101-loss Mariners team from the previous season.
He guided the team with an even-keel approach throughout the season.
But that approach did not work this season.
After losing run-producing third baseman Adrian Beltre and first baseman Russell Branyan to free agency, the Mariners relied on pitching, defense and timely hitting. The pitching has been solid for the most part, but the defense has been so-so and the hitting fell far below what the organization expected, resulting in a 42-70 record as of Monday.
The Mariners held their own in April, posting an 11-12 record despite not having left-hander Cliff Lee, who spent the first month of the season on the disabled list. But the team struggled in May, going 8-19 to fall into the division cellar, and even worse in July, tying a franchise record with 22 losses.
Last Monday, fresh from a winless, seven-game road trip to Chicago and Minneapolis, Zduriencik repeated several times during an impromptu media session on the field that "Don is the manager."
After splitting the first six games of a nine-game homestand, and winning a series for the first time in more than a month, it appeared Wakamatsu's job was a little more secure than a week earlier.
"You get to a point where you have to make a decision," Zduriencik said. "I wasn't prepared to make a decision at that time. There was a lot written and a lot said, but I hadn't settled that myself. I think you get to a point where it's time to make a call and I thought it was necessary to make a call today."
Zduriencik said it wasn't one particular issue that led him to make Monday's decision.
During the course of this disappointing season, batting coach Alan Cockrell was dismissed, Mariners icon Ken Griffey Jr. retired following a reported "napping" incident in the clubhouse during a game against the Angels, and more recently, Wakamatsu and second baseman Chone Figgins got into a verbal exchange in the dugout during a game.
"Why some of the things went on the way they went on and why some of the disappointments existed, everyone has their speculation," he said. "This is about where we're headed. We made a decision today, I arrived at that decision based on a lot of factors. What's important is where we're going with this.
"Sometimes when you get from A to Z, there's not always a straight line," he said. "To take an organization from here to here, sometimes you're going to have those bumps in the road, have rocky waves, things that interfere. There were some things that needed to be changed, and today I made the decision to change them."
The Mariners were expected to play as well, if not better, than last season.
"We entered this season with high expectations," Zduriencik said. "These expectations have not been realized. I accept full responsibility for our Major League team's poor performance this season, and I am determined to make the changes that are necessary as we move forward.
"Our goal is to create a championship-caliber organization that puts us in position to win a World Series. I intend to do that and I will make the necessary changes needed as we move forward.
"Over the past two years, we have made significant progress in our player development and scouting departments. I am very proud of the talent we have accumulated in the Minor Leagues via the draft as well as through trades. I tip my hand to those involved."
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.