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San Francisco 49ers running back Brandon Jacobs carries against the Minnesota Vikings during the first quarter of an NFL preseason football game in San Francisco, Friday, Aug. 10, 2012. (AP Photo/Ben Margot)

SAN FRANCISCO -- Frank Gore had the night off. Brandon Jacobs didn't.

Jacobs, hired this offseason to relieve Gore on short-yardage situations, had a fantastic 49ers debut in Friday night's 17-6 exhibition win over the Minnesota Vikings at Candlestick Park.

All four of Jacobs' carries produced a first down, starting with a fourth-down blast to sustain the 49ers' opening touchdown drive.

"Brandon Jacobs looked really light on his feet," coach Jim Harbaugh said.

Jacobs is lighter, having trimmed 15 pounds off a still-robust frame (6-foot-4, 260 pounds).

See if you notice a trend from his four carries:

  • Fourth-and-one, from the 49ers' 47-yard line: 3-yard run up the middle.

  • Second-and-one, from the Vikings' 41: 23-yard gain around right tackle.

  • Second-and-one, from the Vikings' 9: 2-yard run up the middle.

  • Third-and-one, from the Vikings' 49: 3-yard gain off right guard.

    That's right: All were "and-one" situations. Maybe his name should be "Br-and-one Jacobs."

    "I felt great coming out here," Jacobs said after Friday's debut. "I got a chance to play in front of the home crowd for the first time. It felt a little weird, but it's my home crowd. I loved it."

    A little weird because Jacobs was on the opposing sideline when the 49ers lost to the New York Giants in the NFC Championship game, 20-17 in overtime Jan. 22. Jacobs set the Giants' franchise record with 56 rushing

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    touchdowns the past seven seasons.

    Jacobs pushed those memories out of his mind while he followed solid lead blocks from the 49ers' linemen and fullback Bruce Miller.

    "I love the way they communicate, get things done," Jacobs said. "We're going to have a lot of fun running behind the hogs."

    Jacobs isn't concerned how carries are divided among a crowded backfield.

    While Gore rested Friday, the 49ers relied on Jacobs and the quartet of Kendall Hunter, Anthony Dixon, Rock Cartwright and LaMichael James. Add a few quarterback keepers -- highlighted by Colin Kaepernick's 78-yard, read-option touchdown -- and the 49ers tallied 260 yards on 42 carries.

    "All of our backs ran great tonight, Brandon included," quarterback Alex Smith said. "They all looked great. You know, I think that's a good problem to have."

    Gore is the undisputed starter but could see diminished carries. That might hold true in short-yardage situations, even though he was 5 for 7 in converting third-and-one runs last season; Jacobs was 4 for 6.

    "Whatever they need me to do, I'll do it," Jacobs said last week. "Coaches know my cell number and know where I'm at. They can get me any time."

  • Winds were 20 mph at kickoff, posing more of a challenge to embattled 49ers punt returner Kyle Williams, who botched two returns in the NFC Championship game. Williams responded with 22- and 6-yard returns Friday. "It was kind of swirling, but that's what Candlestick is," Williams said.

    Harbaugh noticed in pregame how the winds would be "especially rough" on Friday's punt returners, Williams and LaMichael James. "We knew that they would be the challenged player on those downs, even more than always," Harbaugh said. "It was good."

    Usual return specialist Ted Ginn Jr. started at wide receiver and was not used on returns.

  • Smith, who went 3 of 3 for 16 yards, said of his 4-yard touchdown pass to Brett Swain: "I love touchdown passes. I didn't throw that great of a ball. ... Swain made a great play down there at the goal line."

  • James said of Kaepernick's touchdown run: "I look up and I see 11 defenders, so I look over and he's gone. Credit to him, he's a fast runner. He made the right read and took off."

  • Vikings quarterback Christian Ponder said Stephen Burton was his third option on their 52-yard completion against Carlos Rogers, who didn't draw safety help from Dashon Goldson.

    Said Ponder: "The safety came down on (tight end) Kyle (Rudolph) and Stevey B. was wide open ... It could have been a touchdown."

  • Kenny Rowe, a member of the 49ers' 2011 training camp, was signed to a two-year contract Saturday in the wake of Aldon Smith's bruised hip Friday night.

    For more on the 49ers, see Cam Inman's Hot Read blog at blogs.mercurynews.com/49ers. Follow him on Twitter at twitter.com/CamInman.