Help is on the way for 49ers’ offense

San Francisco could really use an offensive boost at Houston on Sunday, and the 49ers are hoping Frank Gore and Michael Crabtree can provide one. While most of their teammates took last week off, Gore and Crabtree were among a few players who stayed around team headquarters to work out.

Gore is coming back from an ankle injury, and Crabtree, the rookie first-round pick, will make his first start at receiver. Mike Singletary’s team needs a spark on that side of the ball, particularly coming off a 45-10 loss to Atlanta in Week 5.

Quarterback Shaun Hill told reporters the 6-foot-1, 214-pound Crabtree plays much bigger than he actually is.

“When you see him, you think he’s a little on the short side, but when he’s out there running, getting his hands on the ball, he’s a big target,” Hill said. “Just his stature out there, he seems bigger than if you walk up to him in person. It’s the way he attacks the ball.”

Big Ben is a big problem

They might be in prime position in the NFC North, but the undefeated Minnesota Vikings aren’t in the ideal spot timing-wise to play at Pittsburgh. They could be missing two of their better players: rookie receiver Percy Harvin and Pro Bowl cornerback Antoine Winfield.

Harvin headed home after Sunday’s victory over Baltimore with his arm in a sling to take weight off an injured left shoulder, and Winfield was in a walking boot Monday to protect a bum right foot.

The Winfield injury could be especially costly because the Vikings don’t have anyone who can play corner at his level. They are not ruling him out for the game.

Pittsburgh’s Ben Roethlisberger is adept at identifying weaknesses in a defense, is second to Peyton Manning in completion percentage at 72.5%, and is tied with Manning atop the yards-per-completion chart at 9.1.

Wake up or don’t bother

San Diego blew its best chance to catch up with undefeated Denver in the AFC West by losing at home to the Broncos on Monday night. Now, on a short week, the Chargers should feel even more urgency to handle their business in Kansas City.

The Chargers are 2-3 for the third time in three seasons under Coach Norv Turner.

Even though the Chiefs are in last place in the division and have lost three in a row to the Chargers, this is anything but a breeze for San Diego. Kansas City is coming off a victory over Washington, and played Dallas tough the week before. San Diego swept the series last season, but won both games by just a point.

Jet lag

After winning their first three games, the New York Jets have lost three in a row. Sunday, they come to California -- Mark Sanchez’s first NFL game in his home state -- to face the Oakland Raiders.

The Raiders are coming off a stunning victory over Philadelphia and are itching to prove that outcome was no fluke. Wonder if Rob Ryan, the Raiders’ old defensive coordinator, will provide his brother, Jets Coach Rex Ryan, with any insider tips.

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sam.farmer@latimes.com