"After nine years with the Suns, the organization and I came to a mutual agreement to go in different directions," Gentry said in a statement. "I have the utmost respect for Robert and what he's done with the organization. It's unfortunate that I was unable to accomplish what I set out to do here."
Gentry, who was in the final year of his contract, has been in coaching for three decades, including stints as head coach of the Detroit Pistons, Los Angeles Clippers and Miami Heat.
He came to the Suns as an assistant to D'Antoni and stayed on Porter's staff when D'Antoni left for the Knicks. Gentry was named interim coach when Porter was fired and stayed on as the permanent head coach.
He had some success with the up-tempo style D'Antoni had championed, but the Suns lacked a true scorer and struggled defensively, missing the playoffs the previous two seasons.
When Phoenix opted not to sign Nash with an eye toward rebuilding, Babby and general manager Lance Blanks blew up its roster. Gentry continuously tried new lineups to find a spark, but nothing seemed to work as crowds at the once boisterous US Airways Center started to dwindle.
Gentry recently said it might be better for the team to turn to its younger players and look toward the future, but now it will be without him at the helm.
"It wasn't that we weren't winning enough games so much as a feel that we weren't progressing, that we were regressing," Babby said. "We can't have that. We've got to have our closure moving forward. We didn't feel like we were moving forward and I don't think Alvin felt like we were moving forward."
The Suns don't play again until Wednesday, when they're at Sacramento.