SANTA CLARA — If it’s too soon to conclude A. J. Jenkins is an NFL bust, listening to his words and hearing the voice within would explain why “bust” was an accurate assessment of his rookie season with the 49ers.

Jenkins, in so many words, admits to underestimating the NFL.

Consider all suspicions confirmed by the source.

“It’s a lot faster, man,” Jenkins said Tuesday. “The windows are a lot smaller than in college. (Defensive backs) are a lot quicker and faster. Every catch is going to be more like a contested catch. Mostly in college you’re like wide open all the time. But in the league, you have to really have strong hands because DBs are going to be right on you most of the time.”

Jenkins got schooled in ways he never did during a rich collegiate career at Illinois. Arriving in the Bay Area last spring for rookie minicamps, the first-round draft choice was confident but poorly conditioned. He was puzzled by the playbook and physically overmatched.

One year later, Jenkins is diving into the three-day minicamp at team headquarters with what seems a much better idea of what it takes to survive, much less thrive. He looks bigger, saying his weight is up to around 200 pounds. And he’s drawing praise.

“The last two days of last week he had the two best days he’s had since I’ve been here,” offensive coordinator Greg Roman said.

“A.J. had his best week of football since he’s been a 49er the last four days of OTAs, which was the last week of OTAs,” coach Jim Harbaugh said. “And he continues to build on that.”

A note of caution: Harbaugh and Roman tend to avoid public critiques, opting to speak of their players in reverent tones, and Harbaugh at times is downright defensive. When reporters last spring took note of Jenkins’ unimpressive early showing, implying he was a bust, Harbaugh’s response was an unprompted scolding in Jenkins’ defense.

He said Jenkins had “exceeded expectations” and “will be an outstanding football player in the National Football League.”

The rookie repaid his supportive coach with an invisible season, rarely playing and compiling zero statistics. No catches, no yards.

That’s why his goals in 2013 are so clear. Jenkins must, above all, redeem himself. That would validate Harbaugh’s faith and, moreover, vindicate the risk taken by general manager Trent Baalke, who surprised observers by selecting Jenkins with the 30th overall pick in 2012.

Jenkins, until he proves otherwise, is little more than the most conspicuous blight on the G.M.’s generally impressive draft record. And it stings.

“You just have to tune everybody else out,” Jenkins said, embarking on some self-talk. “Just go into the season and think about your job and your focus. The media covered everything. Being a first-round draft pick, they all want to put this label on you, call you all kinds of things.”

Things such as “bust,” which will define Jenkins if he can’t measure up to league standards — and quickly, considering the condition of San Francisco’s wide receiver corps.

Michael Crabtree, the team’s leading receiver in 2012, could miss the year with a torn Achilles tendon. Randy Moss and Ted Ginn Jr., the team’s most visible speed threats last season, are gone. Mario Manningham is recovering from a knee injury at a slower rate than Kyle Williams, who also is coming off knee surgery.

New acquisition Anquan Boldin is a marvelous weapon, but he alone cannot offset so many absences.

That’s where Jenkins and his huge hands come in. Ricardo Lockette and Quinton Patton are in the mix, but Jenkins realizes he came with higher expectations.

“My mindset going into this offseason was to try to play more anyway, regardless of whether Crabtree was hurt or not,” Jenkins said. “It’s unfortunate that he had an injury, but my mindset didn’t waver at all.”

He says he has a better grasp of the playbook, that he learned a lot watching Moss and continues to get assistance from Boldin. Jenkins claims offseason sessions with quarterback Colin Kaepernick have strengthened their bond.

Though these are important matters in developing individuals and the team, Jenkins also carries the burden of knowing he dropped an opportunity last year.

He bobbled it immediately and never got a grip.

If the 49ers have reservations about Jenkins, and privately they must, they are justified. How could he be even slightly surprised to learn the league of all leagues, featuring the best of the best, is demanding and complex and exacting?

Contact Monte Poole at mpoole@bayareanewsgroup.com. Follow him on Twitter at twitter.com/1montepoole.