SAN FRANCISCO -- Ray McDonald, a highly durable member of the 49ers defensive line, will undergo an MRI exam Monday to determine the severity of the right-biceps injury that forced him out of Sunday night's 34-3 rout of the Houston Texans.

McDonald was hurt during the third quarter en route to the 49ers' only sack of Matt Schaub.

"It felt like a bee sting," said McDonald, who has started every game but one since 2011 at left defensive tackle. "It doesn't hurt, but I'll know more (Monday) when I get an MRI. They say it's not that bad, so we'll see."

Losing McDonald could spell more trouble for an already thin defensive front. Nose tackle Ian Williams has been lost to a season-ending ankle injury, and outside linebacker Aldon Smith is on an indefinite leave for personal reasons. Rookies Tank Carradine and Quinton Dial are on the non-football-injury list for at least another game.

The 49ers initially replaced McDonald with Tony Jerod-Eddie, but Sunday's injury perhaps could prompt them to make another run at veteran free-agent lineman Richard Seymour. The 49ers and Seymour couldn't come to financial terms last month after they expressed interest in the former Raiders and Patriots lineman, according to CBS Sports' Jason La Canfora.

Seymour was a high school teammate of 49ers center Jonathan Goodwin at Lower Richland High in Hopkins, S.C. Seymour has made over $86 million in his career, nearly $30 million more than any defensive tackle in NFL history, according to Sportrac.com. The Raiders voided his contract in February, and he still accounts for nearly $14 million on their salary cap.

  • A week after recovering a fumble in the 49ers' win at St. Louis, Jerod-Eddie notched an interception Sunday night that was his first since high school. "We had a similar play in practice, and I dropped the interception, so it was good to get that one," Jerod-Eddie said of his interception with 25 seconds left in the third quarter.

    Jerod-Eddie kept both footballs from his takeaways and plans to mail them to his mother. Another memento came his way in the locker room, as he was awarded a game ball, along with Tramaine Brock (two interceptions) and Vernon Davis (64-yard touchdown catch).

  • Frank Gore overcame a second-quarter, left-ankle sprain to finish with a team-high 81 rushing yards on 17 carries. He had a season-high 153-yard rushing effort against the Rams last game. Gore did not start the second half in the 49ers' backfield, but he did return to the game and had a 26-yard run in the third quarter. He also had a 26-yard run in the second quarter.

  • Linebacker Patrick Willis' groin injury kept him out a second straight game. He practiced in a limited capacity last week and went through a pregame workout. Willis was replaced in the starting lineup again by Michael Wilhoite, who matched NaVorro Bowman with 11 tackles. Wilhoite added two special-teams tackles in the first half.

  • Cornerback Nnamdi Asomugha missed his second straight game with a hyperextended right knee. He's expected to return next Sunday against the Arizona Cardinals, although his nickel-back job probably has been taken by Brock.

  • Defensive lineman Demarcus Dobbs barely avoided a left-knee injury in the fourth quarter but did get the wind knocked out of him, he said.