Not long after the NFL scouting combine in February, Colin Kaepernick was pondering the obstacles he had overcome in life and the challenges that lie ahead.

Kaepernick decided to define his essence with three words tattooed on his chest:

Against All Odds.

“Things always have been stacked up against me with people telling me what I can’t do, like play college football or now be an NFL quarterback,” said Kaepernick, the 49ers’ second-round draft pick and projected signal-caller of the future. “But I’m a person who rises to the occasion and wants to prove people wrong.”

Talk to those who know Kaepernick best, and they tell of an almost-too-good-to-be-true guy who has traveled an unlikely path to pro football. Humble, sharp and athletic, he is described as an ideal quarterback for new coach Jim Harbaugh to groom.

“The absolute best I’ve ever had,” said Roger Theder, the one-time Cal coach and longtime Northern California QB guru. “He’s a can’t-miss kid. “… He strikes me as the same kind of person as Andrew Luck.”

But unlike Luck, Harbaugh’s protégé at Stanford, Kaepernick never had golden boy prospects. And because he so often was overlooked, Kaepernick (pronounced CAP-ur-nick) carefully has cultivated every perceived slight and channeled them into an almost maniacal drive to succeed.

Despite his good-natured demeanor, the 23-year-old from the Central Valley who rewrote the record book at the only college that offered him a scholarship carries a large chip on his broad shoulders.

“Our family learned that when Colin’s in competitive situations, he changes,” said Rick Kaepernick, his father. “It’s like, ‘Oh, my God, the monster is coming out, and now somebody is going to pay.’ “

But Kaepernick makes clear that the most unusual part of his back story — that he was adopted — is not something he had to overcome.

Living in rural Wisconsin, Rick and Teresa Kaepernick already had two kids — son Kyle and daughter Devon. But they also had lost two boys shortly after birth to genetic-based congenital heart defects. Doctors had advised against having more children.

Eager to have another child, the couple adopted an infant of mixed-race ancestry who had been given up by his teenage mother in Milwaukee. In the years that followed, the Kaepernicks got used to curious glances sometimes directed at the white family with the darker-skinned youngest son.

“We didn’t care about race,” Rick Kaepernick said. “We never have. Colin is not our adopted son. He’s just our son.”

And for his part, Kaepernick seems genuinely mystified when asked if his background somehow helped shaped that me-against-the-world sports mentality. He considers himself blessed to have grown up in a loving family with parents who made sure he was at church every Sunday and never missed one of his sporting events.

“This is just my life,” said Kaepernick, who has had contact with his birth mother but never met her face-to-face.

Early in life he was plagued by upper-respiratory infections that twice led his concerned parents to have him tested for cystic fibrosis. But he outgrew those “… and grew into a remarkable athlete.

At Pitman High in Turlock, where the family had relocated when he was 4 years old, Kaepernick was a three-sport standout. He threw two no-hitters and had a fastball clocked in the low-90s. On the basketball court, the skinny 6-foot-5 Kaepernick once dropped 34 points on the high school team of future Cal star and current Orlando Magic forward Ryan Anderson. (Then again, Anderson got 50 in that game.)

Football, though, was Kaepernick’s first love. He played in a run-oriented Wing-T offense, which meant he flew under the radar. It didn’t help that he weighed just 170 pounds. The schools that did express interest asked him to walk on because they were leery of committing a scholarship to someone who had caught the attention of professional baseball scouts.

“Colin sat there and told every coach: ‘I’m not going to play baseball,’ ” Rick Kaepernick recalled. “He took those rejections as: ‘They don’t believe me. They don’t trust me. They think I’m a liar.’ The only guy who trusted him was Coach Ault.”

Even Nevada coach Chris Ault wondered. But Barry Sacks, a former San Jose State assistant who recruits the Central Valley for the Wolfpack, did not. He was sold after watching Kaepernick play a basketball game with a 102-degree fever.

“He just tore up the court,” Sacks recalled. “I called Coach Ault and said, ‘This is the guy.’ You could see he had all the intangibles. And he can leap tall buildings in a single bound and runs like a gazelle. Guys like this just don’t come along that often.”

Once he got to Nevada, Ault began describing Kaepernick this way: He watches and watches, and watches some more, then, watch out. In Ault’s pistol offense — a hybrid of the shotgun — Kaepernick put up eye-opening numbers after redshirting his first year. He became the first player in NCAA history to throw for more than 10,000 yards and run for more than 4,000.

He earned a degree in business management and the respect of teammates. The Chicago Cubs, who selected him late in the 2009 draft, offered him $30,000 to pitch just one month in Arizona. Kaepernick said no thanks.

“What do I tell my teammates who are back at Nevada working their tails off in July for August camp?’ ” Rick Kaepernick recalled his son saying.

As his NFL draft stock rose this year, so did scrutiny about Kaepernick’s unorthodox throwing motion — which has a long windup.

“I keep reading about his mechanics, but there’s nothing wrong with his release,” said Theder, who has worked with Kaepernick since he was a high school freshman. “He’s got a gun for an arm. He’s a great leader. He’s smart. And he’s tough. You can’t be a wuss if you’re a quarterback. Harbaugh saw all of that.”

Nevada’s Sacks believes Harbaugh and the 49ers, who traded up to select Kaepernick with the 36th pick, also saw something else. In fact, he thinks the ultracompetitive Harbaugh — who was hired in large part to resuscitate the 49ers’ tradition of great quarterbacks — found a kindred spirit in Kaepernick.

“You’d want your son to be like Colin, but when he flips that switch, he’s got a little mean streak in him on the football field,” Sacks said. “And that’s a good thing.”

At the informal 49ers workouts being organized by incumbent quarterback Alex Smith during the NFL lockout, Kaepernick is just returning to form after a post-draft “procedure” for an undisclosed lower-left-leg injury that bothered him his final four games at Nevada.

While he politely declines to discuss that, Kaepernick talks at length about the meaning of elaborate tattoos on both of his upper arms. Each one is centered on Biblical passages that express the idea that God provides everything you need to be successful and, no matter what forces confront you, there is no need to be afraid.

He does more than just wear his beliefs, as well as the belief in himself, on his sleeve.

“I’m not going to be scared of any situation,” he said. “I’m going to be confident, and I’m going to take it head-on.”

Contact Mark Emmons at 408-920-5745.