Byrnes said he will have an MRI taken next week to determine if his left hamstring has healed sufficiently for him to attempt running.
Byrnes initially injured his hamstrings during Spring Training, and they hampered him in the first two months of the season. He went on the disabled list to try and let them heal but wound up tearing the left hamstring not long after returning.
The experience has provided Byrnes with a valuable lesson. So while he desperately wants to play again this year, he knows he can't push it.
"I'm going to be more careful," he said. "It's not worth it. I know what happened last time, and I can't rush the process."
That doesn't mean he's completely ruled out playing again this year. He knows he could not be an everyday player the rest of the way but would like to help if he could.
"If I come back, it would be just to help the team, not to be a hero," Byrnes said. "If I could come back and help the team in any way without risking next year, I'd like to."
Otherwise, he will try to convince the organization to let him play in the instructional league or maybe go to the Dominican Republic to get some at-bats so he can feel ready heading into Spring Training next year.
"This has definitely been a big learning experience for me this year," Byrnes said. "I realize how much I miss playing. There's nothing like being out on that field. I'm looking forward to playing next year. I can't wait to get back on the field."
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.