After being inactive the first 12 games of the season, James has become an impact player for the 49ers in their run to the Super Bowl next week against Baltimore.

His long kickoff return set up the go-ahead score in a late-season win in New England. His experience running the zone read helped Colin Kaepernick rush for 181 yards in a win to open the playoffs against Green Bay. Then James got into the scoring act himself last week, starting San Francisco’s comeback in a 28-24 win over Atlanta in the NFC championship.

“I had a lot to learn,” James said. “I’m still learning. I’m very blessed to be in the situation I’m in.”

Fresh off scoring his first professional touchdown in last week’s win over the Falcons, James is finally fulfilling the expectations the Niners had for him after drafting him in the second round last April following a stellar college career at Oregon.

“From the first time he stepped on the field, he’s been dynamic,” coach Jim Harbaugh said.

Getting on the field was the hard part. James was inactive the first 12 games as he had to adjust to playing from a huddle after being part of Oregon’s fast-paced offense for three years and to learn a much more extensive playbook than he was used to with the Ducks.

James dutifully worked at learning his craft, making his contributions as a scout team running back and receiver and soaking in whatever tips he could get from starter Frank Gore and running backs coach Tom Rathman.

“It was very different,” James said. “I’d never really been in a huddle until I was in high school. Actually, sitting in a huddle and then having to remember it — and not just run it — that was a little bit different for me, but it all works out.”

James got his chance after Kendall Hunter went down with a season-ending Achilles’ injury in New Orleans on Nov. 25. The Niners needed a change-of-pace back to team with Gore and James proved to be a perfect fit.

James was helped by the fact that the Niners offense had changed a bit with the switch at quarterback to Kaepernick from Alex Smith, with the team using more of the read-option plays James was so proficient at in college.

“Once he started getting comfortable, we saw a dynamic football player,” safety Donte Whitner said. “It’s a testament to him to be able to sit on the sideline and be on the developmental squad, as we like to call it, here for so long and actually knowing that you can play football. Actually coming from a big university, playing in a lot of big games, playing a lot of big games and being a big-time player, and having to sit out and be humbled like that, that’s a testament to him and the character he has.”

James rushed for 5,082 yards and scored 58 touchdowns in three seasons for the Ducks, including 471 yards of offense and four touchdowns in two games against Stanford when Harbaugh ran the Cardinal.

Playing for a perennial title contender at Oregon has prepared James for the big stage of the NFL playoffs. He played in three BCS bowl games, including the national championship game against Auburn at the end of his second year in January 2011. He capped his college career by rushing for 159 yards and one touchdown in a 45-38 Rose Bowl win over Wisconsin last January.

“I don’t think there’s too much difference from playing a BCS game at Oregon,” James said of the NFL playoffs. “I think it’s really helped me out playing big games like these. It’s second nature to me. I really don’t think it’s too big a deal.”

He has shown that so far, playing his best on the biggest stage. After making his debut against Miami on Dec. 9 with eight carries for 30 yards, James delivered his most important play of the regular season the following week in a prime-time game at New England.

He returned a kick 62 yards after New England rallied back from 31-3 down to tie the game in the fourth quarter. Kaepernick threw a touchdown pass to Michael Crabtree on the next play as the Niners went on to the win that proved to be the difference in the NFC West race with Seattle.

The big plays have kept coming in the playoffs. He was the decoy on Kaepernick’s 56-yard option keeper that gave San Francisco the lead for good two weeks ago in the 49ers’ playoff opener against Green Bay.

He then had five carries for 34 yards, including a 15-yard touchdown run that started the Niners comeback in Atlanta that has them preparing for the Super Bowl.

“He always has been a smart player,” Gore said. “First, coming in the offense was kind of different. Now the offense is similar to what he did in college. That helps him a lot.”

NOTES: LB Ahmad Brooks (shoulder) practiced for the first time this week. … TE Garrett Celek (foot) is still sidelined.