Helton has been on the disabled list since July 3 with a strained lower back. He began hitting off a tee and participating in short toss a few days ago, but he suffered a major setback when his back pain flared shortly afterward.
Outfielder Ryan Spilborghs, who has been out with a left oblique strain since July 9, said he is beginning to slowly feel better, but no timetable has been set for his return.
This type of injury usually takes four to six weeks to recover from, and Spilborghs said he's still limited to playing catch and doing light workouts in the team's aquatics pool.
"It's just a matter of whether it feels good or not," he said. "I think I'm right on pace."
Despite the absence of two key players, the Rockies have managed to stay afloat in the National League West. Colorado is 12-9 since Spilborghs got hurt and seven games back of the Diamondbacks heading into Monday's series opener of a four-game set against the Nationals.
Jeff Birnbaum is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.