"After a thorough evaluation of OTAs, training camp, games, practice, we felt this was the best move for the team going into the season," Flores said Thursday. "Ryan has done a really good job from a leadership standpoint, from an execution standpoint, and we feel like it's the best move for the team."
Fitzpatrick, 36, has led the Dolphins' quarterback competition all offseason over second-year signal-caller Josh Rosen, but a strong preseason by Rosen made Flores' decision a little tougher.
It seems clear that Flores valued Fitzpatrick's experience, ability to run a new offense and his moxie to rally a young team.
"I know I have more confidence in myself than anybody in the world," Fitzpatrick said. "Sometimes that's a detriment, but a lot of times that works in my favor. I'm always confident in who I am and what I am as a player. This is where I wanted to be and what I worked to get."
Rosen, who suited up for the Dolphins' final preseason game but didn't play against the New Orleans Saints, heard the decision from Flores before Thursday's game and said he doesn't feel great about the decision.
"The battle and competition never stops," Rosen said. "I'll push him every single day for him to get better, and if he doesn't get better, hopefully I'll surpass him at some point. I'm rooting for him more than anyone."
Rosen, 22, admitted he was "drinking water from the fire hose" early in training camp before playing his best football in the second and third preseason games. He declined to directly answer whether he agreed with the decision, but said he believed his improvement, particularly in the past couple of weeks, made the decision harder on Flores.
"On this progression, I think the future will be pretty bright [for me]. I'm excited," Rosen said. "I wouldn't say it's a setback, but it's part of the journey.
"It's only [a matter of] time that this team is mine, but until then I'm going to be as supportive of a backup as I can and push him every single day."
Flores didn't waver when asked if there was a timetable for Rosen to become the starting quarterback. He said Fitzpatrick is his starter and that he's comfortable with that, and there isn't a set amount of time Rosen needs to start this season for him to be evaluated. It's worth noting the Dolphins have a Week 5 bye, which could be an opportunity for a quarterback switch if one is required.
"He's improved greatly over the course of training camp," Flores said of Rosen. "Playing quarterback in this league takes some time. He's in a new offense. I think he'll get there. When? I don't know. A lot of that is up to him. He knows that."
Fitzpatrick will be the 20th quarterback to start for the Dolphins since Dan Marino retired after the 1999 season. Miami has been searching for a franchise quarterback since then.
The Dolphins signed Fitzpatrick to a two-year deal in March with hopes he could be at least a bridge quarterback until whenever they brought in their quarterback of the future. In Rosen, who was the 10th overall pick in the 2018 NFL draft, Dolphins general manager Chris Grier saw what he determined to be a great value on draft weekend in April, acquiring him from the Arizona Cardinals for a 2019 second-round pick and a 2020 fifth-round pick.
Fitzpatrick is set to become the first quarterback to start a game for eight teams.
"I'm excited to get out there and lead this team and do the best I can out there," Fitzpatrick said. "It's a situation I've been in for multiple franchises, and I'll lean on my experience a little bit and try to get the guys out there, everybody on the same page, great communication, and playing with a lot of excitement."