McClendon, only the second manager in Mariners history with a winning record over the course of his tenure, was informed of the decision Friday morning. The 56-year-old has one year remaining on the three-year contract he signed in 2014.
Hitting coach Edgar Martinez and infield coach Chris Woodward have been invited to stay on the Major League staff, while pitching coach Rick Waits and coach Chris Prieto have been invited to remain in the organization in different positions.
Bench coach Trent Jewett, third-base coach Rich Donnelly, outfield coach Andy Van Slyke and bullpen coach Mike Rojas will not be returning.
Dipoto says he has definite ideas of what he's looking for in a new manager, and that prior experience as a Major League skipper isn't a necessity.
"Positive energy, interaction with players, a good baseball background, a teacher, someone who can create a plan and lead people," he said. "In many ways, a manager's position is as much about creating an environment as it is about Xs and Os. Too much is made of analytics. That's a little overblown. It's more about environment, leadership and energy."
Dipoto does have an interest in sabermetrics and clashed with Angels manager Mike Scioscia in Anaheim about implementing analytics, but he said his only desire is to find a manager who is "open-minded and receptive" to different ideas.
"I like for everyone to use information in a positive way," he said. "You can't make decisions without information. It is not all about the data you're provided or what you're seeing with your eyes, it's somewhere in between. A prerequisite will be to find someone who can balance those in an effective way."
McClendon posted a 163-161 record in two years in Seattle, including an 87-75 mark in 2014 that was the Mariners' first winning season since '09. But after falling one game shy of an American League Wild Card spot last year and raising expectations for a playoff push in '15, the Mariners went 76-86 this year and finished fourth in the AL West.
Lou Piniella is the only other Mariners manager to have a winning mark over the course of his career in Seattle, going 840-711 (.542) from 1993-2002. McClendon was the 16th full-time manager in the franchise's 39-year history.
Dipoto said he has a short list of candidates already in mind, and that he would begin pursuing candidates as soon as they are available, with the postseason currently underway.
Tim Bogar, who was bench coach with the Rangers last year and went 14-8 as their interim manager following Ron Washington's late-season departure, is believed to be a top contender. Dipoto hired Bogar this past year as a special assistant to the general manager in Anaheim, and the two played together on the Mets from 1995-96.
Among experienced managerial candidates available are former longtime Padres skipper Bud Black and former Cubs manager Rick Renteria, who interviewed briefly for the Mariners spot when McClendon was hired two years ago but was already lined up with the Cubs at that point. Renteria was dismissed by the Cubs when Joe Maddon became available after the 2014 season.
McClendon compiled a 499-607 record in seven seasons as a manager for the Mariners (2014-15) and Pirates ('01-05). He worked as a coach on Jim Leyland's staff with the Tigers from '06-13, including the final seven seasons as the hitting instructor.
Dipoto has already informed numerous front-office members that their contracts won't be renewed after Nov. 1, including assistants to the general manager Ted Simmons, Joe McIlvaine and Pete Vuckovich and long-time pro scouts Duane Shaffer and Joe Nigro. Additionally, Chris Gwynn, the team's director of player development, has resigned from that post after four seasons as the club's farm director.