Byrd said that he started noticing the pain about six days ago and tried to play through it before finally conceding to the DL.
"I'm mentally strong, so I was able to play through it," Byrd said. "And it's just not getting any better. So 15 days is early in the year right now. It's the perfect time to try to get it to clear up."
Byrd, who was disheartened by the injury, feels that it may be a result of overwork.
"It's very disappointing," he said. "I train all offseason to try and keep my body in perfect shape. I maybe overworked it a little bit, and when I started feeling it, I didn't back off when I should have."
According to manager Ron Washington, the team could have let Byrd play through the injury but did not think it would be worthwhile.
"The only way that's going to settle itself down is for Marlon to be put in a situation where he can't do anything," Washington said. "So we'll give him a few days where he doesn't do anything and then start rehabbing it and see how it comes."
Washington is hopeful that Byrd will be able to return by the end of his stint on the disabled list, which would be during the first week of May. The 30-year-old Byrd is hitting .129 (4-for-31) in 13 games as part of an outfield rotation for the Rangers.
With Byrd on the DL, the Rangers purchased the contract of infielder German Duran from Triple-A Oklahoma. To make room on the 40-man roster, Texas recalled right-hander Thomas Diamond and placed him on the 60-day DL.
The 23-year-old Duran was in the starting lineup for Thursday's tilt, making his Major League debut. He started at third base in place of Hank Blalock, another Ranger who is dealing with an injury. Blalock left Wednesday's game in the 10th inning with a sore back, but Washington said that the condition will not require a trip to the disabled list, as the third baseman is already making progress.
"His back is still locked up, but he looks much better today than yesterday," said Washington. "The medical staff seem to think that in a couple of days he'll be ready to get back on the field for the series in Boston."
Michael Young was also missing from Thursday's starting lineup because of a sore right calf. Washington said that keeping Young out of the lineup was a precautionary move but that the shortstop would be ready to play on Friday against Boston.
Washington noted that both Blalock and Young would be available as pinch-hitters on Thursday.
David Singh is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.