Johnson is in the midst of a strong comeback year after signing with Arizona late in training camp. He is fourth in the NFL in rushing with 814 yards.
His backup, Andre Ellington, also was hurt in the game. Arians says Ellington has turf toe. Cornerback Jerraud Powers also left the game with what Arians said was a strained calf.
Johnson signed a one-year contract at the veteran’s minimum of $870,000 with a deal loaded with incentives. He has said he thought teams stayed away from him after he was shot while riding in a van in Orlando, Florida, one early March morning. A passenger in the van was killed and another was injured. Johnson still has the bullet in his shoulder.
Johnson has said he believes he would have been killed had he not leaned over to check a text message on his phone. He said he was ordered to bed rest for six weeks and lost 25 pounds before going to Los Angeles to work his way back into football shape.
When Ellington was nursing an injury, Johnson took the starting running back job with strong early performances.
In the third game of the season, at home against San Francisco, he rushed for 110 yards on 22 carries. Later, at Detroit, he gained 103 yards on 22 attempts. He gained a season-high 122 yards (on 18 carries) in a Monday night game against Baltimore and followed that with a 109-yard game on 22 rushes at Cleveland. His production had dipped in recent games.
In Sunday’s game, he carried 12 times for 17 yards before limping off with the injury.
Johnson, 30, made the Pro Bowl three times and topped 1,000 yards rushing in each of his six seasons with the Tennessee Titans. In 2009, he led the NFL in rushing with 2,006 yards. He played one season for the New York Jets before being released.
The loss of Johnson would be a blow to an Arizona team that, at 9-2, has the second-best record in the NFL.
Without Johnson and Ellington out, rookie David Johnson would move into the No. 1 running back spot. David Johnson scored Arizona’s first touchdown in Sunday’s 19-13 victory with a 5-yard run.
The rookie leads the team with eight touchdowns, but has had trouble holding onto the ball at times.
"David is working on his ball security. He’s much better," Arians said. "He still struggles sometimes out in space, reading hots and blitzes, like most rookies do, but he did a great job on that goal line by putting his foot into the ground and making that run for the touchdown. I have all the confidence world in him and him starting."
Stepfan Taylor is the only other running back on the active roster, so the team probably would elevate Kerwynn Williams from the practice squad.
Justin Bethel would move into Powers’ spot.
Safety Tyrann Mathieu called the possible loss of Powers "huge."
"But we have a guy named Justin Bethe," Mathieu said. "I feel athletically he’s just as gifted as Pat (Peterson). So this is his moment to step up and challenge himself and I know the rest of the defense will challenge him to be ready."
To shore up the depth in the secondary, Arians said wide receiver Brittain Golden would practice some at the nickel cornerback position this week. Golden, an important player on special teams, has played some at cornerback in the past.
Arians gave the players the day off as "Victory Monday," but Peterson, the defensive team captain, called a defense-only meeting to go over mistakes made against the 49ers.
"We’re all reminded of last year," Mathieu said, referring to defensive letdowns as the team lost six of its last eight games. "We don’t want to have that relapse again. It’s very important for us to stay focused, continue to find ways to win games."
He said the entire defense showed up for the meeting.
"I think it says a lot about Patrick and his leadership," Mathieu said. "When he says something, people do it."