Asked to highlight notable aspects of the Colts' offense that didn't involve quarterback Andrew Luck, 49ers linebacker NaVorro Bowman was at a bit of a loss Wednesday.

"It's really just No. 12, man," Bowman said. "I feel like they feed off of him and he runs pretty much every phase."

A few hours after Bowman's analysis, Indianapolis added a potentially dynamic second dimension: running back Trent Richardson.

The Colts surrendered a coveted first-round pick to acquire Richardson, the No. 3 overall pick in the 2012 draft who is expected to play plenty when Indianapolis meets the 49ers at Candlestick Park on Sunday.

On Thursday, Colts head coach Chuck Pagano, who termed his 5-foot-9, 228-pound back a "rolling ball of butcher knives," said he would like to see an immediate return on the franchise's investment. Pagano said Richardson would be given as much work "as he can handle."

"We did not bring him in here to, I guess, be the water boy on Sunday," Pagano said. "He'll be ready to roll."

The 49ers learned of the acquisition during their practice Wednesday afternoon, and an assistant quickly compiled a video of Richardson's runs. San Francisco's defense studied the video Thursday morning, and inside linebacker Patrick Willis came away impressed.

"You don't know why Cleveland would let go of a guy like that," Willis said.

For his part, rookie safety Eric Reid didn't need an introduction to Richardson's bruising style. At LSU, Reid squared off with Richardson, then at Alabama, twice in 2011. Richardson had 276 total yards and a touchdown in those games.

Reid said it's wise to gang-tackle the 2011 Doak Walker Award winner.

"I don't think (Richardson) necessarily changes (our) game plan," Reid said. "You just know that it might take a bit more oomph to get him on the ground."

Despite his pedigree, Richardson has a middling yards-per-carry average (3.5) in 17 career games. This season, he rushed for 105 yards on 31 carries in his first two games with the Browns. As a rookie, he rushed for 950 yards, averaged 3.6 yards a carry and set a franchise rookie record with 11 touchdowns.

In Indianapolis, he figures to benefit from pairing with Luck, the No. 1 overall pick in 2012 who set an NFL rookie record with 4,374 passing yards. With the Browns, Richardson was surrounded by a less-than-stellar supporting cast: Quarterback Brandon Weeden ranked 29th in the NFL in passer rating in Cleveland's 5-11 2012 season.

"People can't just stack nine (defenders) in the box" anymore, Richardson said. "You think you're going to stack nine in the box, Andrew's got an arm for you."

Niners defensive coordinator Vic Fangio said it wouldn't surprise him if Richardson plays as many as 90 percent of the Colts' offensive snaps. Fangio believes Richardson will be familiar with the Colts' pass-protection schemes, many of which mirror those he learned in Cleveland.

The reason: Indianapolis offensive coordinator Pep Hamilton has been influenced by Cleveland offensive coordinator Norv Turner after they were assistants together with the 49ers in 2006.

Fangio doesn't expect the Colts to unveil a dramatically different offense Sunday. But he does anticipate seeing a bit more of their ground game after Luck ranked fifth in the NFL in passing attempts last year.

"They just may hand it off more than they have been," Fangio said. "They got a great running back to give it to. It's even more reason for them to have balance in their offense, which I think they're striving to do anyway. So, it just gives them an upgrade at running back, and we're going to see him."

Career stats Trent Richardson, drafted third overall by the Browns in 2012, played 17 games in Cleveland before being traded to Indianapolis on Wednesday: RUSHING RECEIVING Car Yds Avg TD Rec Yds Avg TD 298 1,055 3.5 11 58 418 7.2 1