Span went to Dallas on Thursday to see a back specialist, who gave him the good news.
"I was a little nervous, but I was happy that the doctor gave me a clean bill of health," Span said via telephone.
While he is on the DL, Span will continue to strengthen his back muscles and his abdominal muscles, which were surgically repaired during Spring Training. The abdominal muscles are still weak, according to Span.
Span is expected to undergo physical therapy Saturday and have cortisone injections in his back. There is no timetable as to when Span will return to the field.
"[The doctor] thought once I give my body some rest that I should be fine," Span said. "He said it might be one of those instances where the rest of the season might be a battle. Once the season is over with and I have a full offseason, I should be fine."
Despite dealing with injuries during the first half of the season, Span was productive at the plate, hitting .304 with 37 runs scored, a .367 on-base percentage and 11 stolen bases.
"It's been a grind," Span said. "I have to give all the glory to God, because it's the first time that I didn't have an offseason [due to sports hernia surgery]. Even though I didn't train for the season, it's probably one of the best starts I've had. It's a big testament to hard work and just my will in wanting to be the best and helping this ballclub."
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.