From TR Sullivan:

Whoever it is, the Rangers will look for someone who has strong communication skills with players. In the end, Showalter lost his job because, Hicks said, the players had stopped listening to his message and had tuned him out.

"It was just our belief that Buck was unable to be as effective with the players as he had been a few years ago and needed to be in order to win," Hicks said. "The thing about sports is, in the end, the win-loss record is staring at you every day.

"In the end, J.D. was very persuasive that with the nucleus of players, if we were going to win, we needed a fresh approach. Most managers or coaches, whatever the sport, there is a period of time where your message is effective."

I believe Daniels stated in his press conference he didn't talk with the players.  So how did he arrive at the conclusion the players "had tuned Showalter out?"  Showalter's departure by itself is not of great concern, except for the fact the Rangers are going to spend $6 million over the next three years to pay off his contract.   The standard excuse for not expanding payroll is the Rangers cannot afford it.  

Showalter stated in Sullivan's article the only player to complain to him was Blalock who didn't like being benched against left handers, (even though he was awful against them.)  Daniels stated his expectation was the team was capable of winning 85 to 90 games.  So Showalter is being fired because the Rangers lost five games more than they should have?

Daniels  acknowledged Oakland was a better team than Texas, so is Ken Macha the reason Oakland is better or could it be that Billy Beane is a better general manager?  Like other Daniels decisions, firing Showalter was a kneejerk reaction to a disappointing finish and a waste of money.  There may be better managers out there than Showalter, but finding him isn't going to significantly close the gap between Oakland and the Rangers.