About an hour into Sunday's workout, Moreno caught a pass in 7-on-7 drills and turned upfield when his right leg buckled. He grimaced as he hopped into Broncos headquarters for tests.
A league source told NFL Network insider Jason La Canfora that Moreno pulled his right hamstring and will be out at least two weeks. It's a potentially easily aggravated injury, however, so Moreno's recovery time will be re-assessed as he continues to rest and rehabilitate.
Buckhalter was injured about 10 minutes later during the same drill and limped off on his own. The Denver Post reported that when Buckhalter experienced tingling in his extremities, he was sent to a local hospital as a precaution, but he was quickly released after his head, neck, back and spine were checked.
According to La Canfora, Buckhalter will be evaluated daily and could return to practice in a matter of days.
Broncos coach Josh McDaniels, who 48 hours earlier traded veteran running back J.J. Arrington to the Philadelphia Eagles for special teams stud Joe Mays, said he didn't know the extent of the running backs' injuries.
"Certainly, you don't want to see two of your guys that you really count on at the same position come off the field on the first day of training camp," McDaniels said.
"One guy goes down, a guy moves up," Ball said. "Chance to get more reps, get on film and impress the coaches."
The Associated Press contributed to this report.