DAVIE, Fla. (AP) -- Fullback Matt Quillen became the third player to quit the Miami Dolphins' training camp, and coach Tony Sparano conceded he could be the reason for the defections.
"It might be me," Sparano said with a chuckle Monday. "I'm not for everybody."
All of the players who have left were long shots to make the team. Quillen signed Thursday and lasted only one practice.
"It has an awful lot to do with passion," Sparano said. "This is a credit to the other guys that are in that locker room: What they are doing right now is really hard.
"If your heart isn't in what you're doing, it does not take long with the heat, with the contact, with the intensity of what we're doing out here, and the way we're doing it, to figure out that maybe this isn't for you."
Once a player reaches that conclusion, it's better for the team that he call it quits rather than keep practicing, Sparano said.
Tackle SirVincent Rogers and safety Ethan Kilmer left camp earlier.
The Dolphins signed two players Monday: kicker Connor Barth and receiver James Robinson. Barth made the Kansas City Chiefs as a rookie free agent in 2008 and made 10 of 12 field goals, but they waived him July 28.
Incumbent Dan Carpenter remains a strong favorite for the kicking job.
Robinson, a native of Fort Lauderdale, Fla., played in 13 games last year for Toronto of the Canadian Football League, making 25 receptions for 381 yards and one touchdown.