SANTA CLARA -- Not only are the 49ers without the top three running backs with which they started the season, their top three cornerbacks also won’t play against Falcons quarterback Matt Ryan, who leads the NFC in passing yards.
Not only was Kenneth Acker (concussion) declared inactive as expected, fellow starter Tramaine Brock (deep shin bruise) was told two hours before the game that he wouldn’t play and didn’t seem pleased by the decision. A third cornerback, Keith Reaser, suffered a sprained ankle in St. Louis last week and practiced sparingly.
That means second-year player Dontae Johnson will start at one spot and Marcus Cromartie, who had been on the practice squad to this point, will start at the other spot. The only other cornerback available is Chris Davis, whom the 49ers signed last week and who also was elevated from the practice squad. Safety Jimmie Ward could play the position in a pinch.
Ryan has 2,399 passing yards, third best in the NFL. His top target, receiver Julio Jones, leads the league in receiving yards.
At running back, Kendall Gaskins will start his first-ever NFL game. He was on the practice squad just 10 days ago. Newcomers Shaun Draughns and Pierre Thomas also are likely to be worked into the game.
At receiver, Anquan Boldin will miss his second straight game. Bruce Ellington, Quinton Patton and Jerome Simpson will be rotated opposite Torrey Smith
Elsewhere, tight end Garrett Celek is active after suffering a concussion against the Rams. Nose tackle Mike Purcell -- who starred in the preseason -- also is active for the first time this season.
WR Anquan Boldin
RB Carlos Hyde
CB Kenneth Acker
CB Tramaine Brock
CB Keith Reaser
G Ian Silberman
G Brandon Thomas
CB Robert Alford
S William Moore
LB Justin Durant
C James Stone
T Bryce Harris
WR Leonard Hankerson
DE Malliciah Goodman