Dallas (ankle) was a non-participant in Wednesday's practice, John Boyle of the Seahawks' official site reports.
Dallas was diagnosed with a Grade 3 ankle sprain following this past Sunday's 20-15 win over Washington, so his absence from practice isn't surprising. He should be considered a long shot to play in Week 16 against the Rams. If he's indeed out, Chris Carson (foot), Carlos Hyde and Rashaad Penny will be the only running backs suiting up.