San Francisco 49ers head coach Jim Harbaugh did not have an update on injured defensive lineman Ray McDonald Monday, after he suffered an apparent biceps injury on a third-quarter sack in the team's 31-point blowout of the Houston Texans Sunday night.
The MRI results are due Monday afternoon, Harbaugh said.
A complete tear of the bicep could end McDonald's season and require four to six months of recovery. A partial tear could take three to six weeks.
Losing McDonald for a prolonged period doesn't bode well for the defensive front that's already been without starters Patrick Willis, Aldon Smith and Ian Williams.
But help could be on the way in the form of two rookies Tank Carradine and Quinton Dial. Both players are currently on the reserve/non-football injury list.
By being designated on that list following training camp, Carradine and Dial will be cleared to practice following next Sunday's game against the Arizona Cardinals. Once they begin practicing, they will have a 21-day window to be placed on the 53-man roster or injured reserve, making a player ineligible to play this season.
"Based on their health and their practice capability, their readiness to help on game day. All those things will go into determining when they'll exactly be headed back to the 53," Harbaugh said.
Carradine, a second-round pick from Florida State, saw his draft stock fall from being a potential first rounder after suffering a torn ACL in a game last November. Dial was taken in the fifth round out of Alabama and spent the offseason recovering from a toe injury.
Tony Jerod-Eddie and Demarcus Dobbs would figure to fill in for McDonald should he be out next week. Both players have seen a decent share of snaps this year after McDonald and Justin Smith received nearly every snap in 2012. When Smith was out with a torn triceps injury late in the year, departed free agent Ricky Jean-Francois took his place.
Other players on the reserve/NFI list include Eric Wright and Mario Manningham, who Harbaugh said he also expects to begin practicing next week.
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