Fields was promoted to the Chargers' active roster Saturday, Michael Gehlken of the San Diego Union-Tribune reports.
Fields joins the 53-man roster in place of cornerback Craig Mager, who was placed on injured reserve Saturday. The young linebacker has not played a down this season, and his lone game experience was a brief stint with the Redskins in 2015. He'll likely only see the field Sunday if the Chargers suffer a number of injuries in the linebacking corps unless he mixes in on special teams.