Rams running back Todd Gurley will test 49ers

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The 49ers already have enough headaches, but they’ll have to deal with a major migraine Sunday: Rams rookie running back Todd Gurley.

Three starts into his NFL career, Gurley, 21, has more runs of 40-plus yards (three) than 29 NFL teams, more runs of 20-plus yards (six) than 24 teams and has become the youngest player to rush for at least 125 yards in three consecutive games since at least 1960.

Those superb stats look superhuman when considering this: Gurley missed the season’s first two games, didn’t have more than six carries in a game until Week 4 and has just three career starts because … he is 11 months removed from sustaining a torn ACL.

What’s next? Maybe he’ll leap the Gateway Arch in a single bound when he — you know — gets fully healthy. Gurley ditched his knee brace for the first time Sunday and had 163 total yards and two touchdowns in a 24-6 win over the Browns.

“I don’t think he’s 100 percent,” St. Louis head coach Jeff Fisher said. “I think it takes time … but he’s pretty close to it. And if he’s less than 100 percent, whatever percent he’s at right now is pretty impressive.”

The Rams’ risk is being rewarded. They selected Gurley with the No. 10 pick, despite his injury and the fact that he plays a position that has been devalued in the NFL. Gurley became only the second running back taken with a top-10 pick since 2011, and just the sixth selected in the top 10 in the past 10 drafts.

The Rams weren’t the only team smitten. The Seahawks reportedly placed Gurley at the top of their draft board.

St. Louis Rams running back Todd Gurley runs with the ball during the first quarter of an NFL football game against the Cleveland Browns Sunday, Oct. 25, 2015, in St. Louis. (AP Photo/Tom Gannam) St. Louis Rams running back Todd Gurley runs with the ball during the first quarter of an NFL football game against the Cleveland Browns Sunday, Oct. 25, 2015, in St. Louis. (AP Photo/Tom Gannam) Photo: Tom Gannam, Associated Press Photo: Tom Gannam, Associated Press Image 1 of / 1 Caption Close Rams running back Todd Gurley will test 49ers 1 / 1 Back to Gallery

Gurley was coveted because of his comic-book-hero qualities. He’s built like a power back (6-foot-1, 227 pounds) and moves like a sprinter — which he is. He was a state champion in the 110-meter hurdles at Taboro (N.C.) High School, reached the semifinals in the event at the 2011 World Youth Championships in Lille, France, and had the seventh-fastest time in school history in the 60-meter hurdles at Georgia in 2013.

In college, Gurley dabbled in track and dominated in football. In 30 games, he averaged 130 total yards, scored 44 touchdowns and had a school-record 6.4 yards a carry.

Niners defensive tackle Quinton Dial, who played at Alabama, has a sense of what awaits the 49ers (2-5) when they visit St. Louis (3-3) on Sunday. In the 2012 SEC Championship Game, Gurley had 122 yards on 23 carries and scored two touchdowns in the Tide’s 32-28 win over the Bulldogs.

“We’re just going to have to come to work when we tackle this guy,” Dial said. “He’s got some ability to make you miss and he’s fast as hell.”

St. Louis linebacker James Laurinaitis is happy he doesn’t have to tackle Gurley, noting it requires “big-boy pads” to bring him down. Gurley is averaging 3.5 yards after contact, which is third in the NFL, according to Pro Football Focus.

“We all saw the highlights when he was in college,” Laurinaitis said. “We thought we had a heck of a player. You just didn’t really know what kind of impact he’d have his rookie year coming off the injury. But you knew the way the coaches, and the staff and the scouts all talked about Todd. They said he was the best running-back prospect coming out since Adrian.”

That would be Minnesota’s Adrian Peterson, the 2012 NFL MVP who is the third-fastest in NFL history to reach 10,000 rushing yards. It’s premature to place Gurley in Peterson’s class, but he’s already connected with a Hall of Famer. Gurley is the first rookie since Eric Dickerson in 1983 to rush for 125 yards and average 5-plus yards a carry three times in his team’s first eight games.

Gurley ranks second in the NFL in yards per attempt (6.0) and leads the league in fourth-quarter rushing yards (213). His most impressive feat? He has brought energy to the Edward Jones Dome, an often-lifeless stadium that could be vacant in 2016 if the Rams make a much-discussed move to Los Angeles.

On Sunday, however, Gurley raised the decibel level as he ran over the Browns.

“We had to quiet (the fans) down when the offense had the ball,” Fisher said, “because they were chanting ‘Gurley.’”

Eric Branch is a San Francisco Chronicle staff writer. E-mail: ebranch@sfchronicle.com Twitter: @Eric_Branch

Great starts

A look at some of the greatest rookie seasons by running backs in NFL history:

Top 5

Year Player Yards Avg. TDs 1983 Eric Dickerson, Rams 1,808 4.6 18 1981 George Rogers, Saints 1,674 4.4 13 2012 Alfred Morris, Washington 1,613 4.8 13 1979 Ottis Anderson, Cardinals 1,605 4.8 8 1999 Edgerrin James, Colts 1,553 4.2 13

Others of note

Year Player Yards Avg. TDs 2002 Clinton Portis, Broncos 1,508 5.5 15 2000 Mike Anderson, Broncos 1,487 5.0 15 1989 Barry Sanders, Lions 1,470 5.3 14 1978 Earl Campbell, Oilers 1,450 4.8 13 2007 Adrian Peterson, Vikings-x 1,341 5.6 12