The Diamondbacks made the move Tuesday over the objections of Byrnes, who felt his sore hamstrings had improved.
"I'm not thrilled about it, but that's just my competitive nature," he said. "I wanted to keep playing. It's something I've been dealing with for a month now, and in my mind I feel like I've gone through the worst of it."
Manager Bob Melvin said he and general manager Josh Byrnes made the decision that rest was required for the outfielder to regain the ever-hustling style that is his trademark.
"He's not 100 percent, in my opinion not really even close. Both hamstrings are bothering him," Melvin said. "He needs all his weapons to be Eric Byrnes, and we need him 100 percent. We need him to play a certain way and he's not able to do it right now."
Byrnes is batting just .219 with six home runs and 23 RBIs but refused to blame his hitting struggles on his sore legs.
"It definitely didn't help, but that's something I've gone through before," Byrnes said of the slump. "It's the reality of baseball. I mean, I went 9-for-95 before. I've dealt with things like this before. For me to just point at my legs and my hamstrings and say that was the cause, I won't do that."
He has been a streaky hitter throughout his career.
"The flip side is I'd like to think when I get hot I get as hot as anybody in baseball," Byrnes said. "Like it or not, that's the type of player I've been."
Melvin, though, said the injury has to affect Byrnes at least psychologically at the plate.
"You can't help thinking a little bit 'How am I going to get out of the box? How am I going to get down the line?'" Melvin said. "So I think it plays into it a little bit. I don't think he'll admit that."
Last year, Byrnes was fourth in the National League with 50 stolen bases and was caught just seven times. This year, he has four steals and has been thrown out three times.
The hamstring problems began when he was running with center fielder Chris Young a few days before the start of spring training. As that soreness worsened, he began overcompensating, and that led to the other hamstring hurting.
Byrnes said he'd spent five hours a day on the training table just to be able to play.
The Diamondbacks recalled outfielder Alex Romero from Triple-A Tucson to take Byrnes' roster spot after giving some consideration to bringing up veteran Trot Nixon instead. Jeff Salazar was in left field for Tuesday night's game against San Francisco. Melvin said he planned to use utility man Chris Burke some in left, as well.
Byrnes found a home in Arizona after an itinerant major league career with stops in Oakland, Colorado and Baltimore, becoming one of the Diamondbacks' most popular players with his offbeat personality and ever-hustling on-field style.
He signed a three-year, $30 million contract last August as a reward for a career year in which he batted .286 with 21 home runs and 83 RBIs to go with his 50 steals.
Byrnes planned to return to his Bay Area home this week to work with his chiropractor Dick Athens. He said he doesn't expect to spend one minute beyond the 15 days before returning to the lineup, although he acknowledged that won't be his call.
"Look, they made the decision. It wasn't up to me," Byrnes said. "I totally understand. They had to do what they felt was best for the team, and I think ultimately it will help me as well."