With Colin Kaepernick dealing with tightness in his throwing shoulder and Thaddeus Lewis out for the season with a knee injury, San Francisco signed the free-agent quarterback Christian Ponder to a one-year contract.
Ponder, 28, has not appeared in an N.F.L. game since October 2014, with the Minnesota Vikings.
The 49ers were down to two healthy quarterbacks, Blaine Gabbert and Jeff Driskel, as the team traveled to Denver for two joint practices with the Broncos ahead of their preseason game on Saturday.
BILLS DEFENSIVE TACKLE IS SUSPENDED The N.F.L. suspended Buffalo defensive tackle Marcell Dareus for the first four games of the season for violating the league’s substance-abuse policy.