The firing of Don Wakamatsu and three other coaches came as little surprise to Mariners fans, and blog Lookout Landing is supportive of the move:
Ultimately, what it comes down to is that, while I think and the front office seems to think that Don Wakamatsu could be a quality big league manager, there was good reason to doubt his ability to be a quality big league manager of the Seattle Mariners, and for that reason he has been let go. Though he and the rest of his coaching staff are not the reason the team is where it is, he has nevertheless failed to act as a capable leader of a sinking team, and if the Mariners believed that the situation between Wakamatsu and many of the players was irreparable, then they made the right call. It's never about assigning blame. It's about doing the best you can with what you have.
Wakamatsu may not be a bad manager, but he became the wrong manager for the Seattle Mariners. Once that became clear, there was nothing else to do but let him go.