Dahl was hurt on a helmet-to-helmet hit with Raiders running back Darren McFadden in last week's 16-14 loss at Oakland. Rams coach Steve Spagnuolo said Dahl showed symptoms after a light workout Wednesday and, after a day of rest, will try again Friday.
Dahl said he was still light sensitive and was experiencing other post-concussion symptoms.
NFL Network insider Jason La Canfora reported Sunday that Ryan is suffering from post-concussion symptoms, according to a league source.
Ryan missed the game against the Raiders and spent one night in the hospital suffering from what the team called migraines. He also missed Thursday's practice to be examined by another doctor, but he hasn't been ruled out for Sunday's home game against the Washington Redskins.
The Rams also held out wide receiver Laurent Robinson from practice Thursday because of a foot injury.
The Rams continued looking at receivers and return men Wednesday, La Canfora reported. The team worked out Yamon Figurs, recently cut by the Oakland Raiders, and veteran Reggie Brown, according to a league source. Free-agent running back Kevin Jones visited the team Wednesday as well.
The Associated Press contributed to this report.