Only three of the 26 running backs selected in the 2005 NFL Draft are still in the league.

Furthermore, only one of them stands as his franchise leader in three major stat categories: carries, rushing yards and rushing touchdowns.

Enter San Francisco 49ers workhorse Frank Gore.

The former third-round pick, who was the sixth running back drafted in 2005, has more rushing yards than any of his draft class counterparts and still carries the chip on his shoulder from being passed up at the draft. Gore, a four-time Pro Bowl running back, has gained 8,839 rushing yards in eight seasons.

"Nobody expected me to be in the league this long," Gore told 49ers.com after a recent workout at 49ers headquarters.

Only Brandon Jacobs and Marion Barber have more touchdowns than Gore and both remain unsigned. With just six more touchdowns this season, Gore will lead his draft class in that category too.

The recently turned 30-year-old running back has been on a blistering pace to start his career with the 49ers and doesn't plan on slowing down any time soon. Gore has eclipsed the 1,000-yard rushing mark in six out of eight seasons. He finished 2012, his fourth Pro Bowl season, with 1,214 rushing yards. With 37 more yards on the ground, Gore will pass Roger Craig to rank second all-time on San Francisco's yards from scrimmage list.

At that point, Gore would only trail Hall of Fame wider receiver Jerry Rice.

It's been an already historic career for Gore in San Francisco. The hard-nosed running back slipped to the third round in 2005 because of medical concerns about his knees. Looking back, the draft-day slide might have been a blessing in disguise. Gore came into the NFL motivated to prove critics wrong.

"Every year in my career, it's been 'when' and 'if' I'll slow down," Gore said. "I look at it as a challenge."

Gore hasn't just accepted the challenge, he's used it to become one of the NFL's top running backs. After turning 30 on May 14, there's still plenty Gore wants to accomplish.

"I want to show I'm not going by what people say about being a certain age - when you're 29 or 30, you can't do it anymore," Gore said. "As long as I'm working, healthy and able to play this game, I can do a great job."

When Gore came to San Francisco, he split carries with running backs Kevan Barlow and Maurice Hicks. Neither Barlow or Hicks were proven NFL veterans, forcing Gore to find his own example of how to be successful.

"I didn't have anybody to look up to," Gore said. "I'm not talking bad about any of the guys who were here before me. I just didn't have a guy who had success in the league."

Instead, Gore has provided that example for the rest of the 49ers running backs. Anthony Dixon, Kendall Hunter and LaMichael James constantly speak highly, not only for his ability on the field, but what he means to the entire group off the field.