49ers' Daniel Kilgore injures leg

DENVER -- San Francisco 49ers center Daniel Kilgore suffered a lower left leg and ankle injury in the third quarter of the team's 42-17 loss to the Broncos on Sunday night, something coach Jim Harbaugh said "might be a break."

If it is a broken leg, Kilgore would be out an extended period of time, putting the Niners' already makeshift line in further flux as they head into a badly needed bye week.

"It's always tragic to lose a player," said quarterback Colin Kaepernick. "I don't know exactly what it is right now. Hopefully it's not something that is season-ending."

The backup center, undrafted rookie Dillon Farrell, also came out of the game for a spell in the fourth quarter after rolling an ankle, though Harbaugh said he should be fine.

The 49ers were already without left guard Mike Iupati, who suffered a concussion Monday night at the St. Louis Rams and was not cleared to play in this game.

After Farrell left the game, the Niners O-line was this: left tackle Joe Staley, left guard Jonathan Martin, center Joe Looney, right gurad Alex Boone, right tackle Anthony Davis.

Third-round draft pick Marcus Martin was the backup center in camp, but he injured his left knee in the 49ers' third preseason game and is still working his way back.

The 49ers surrendered a season-high six sacks to the Broncos.