SANTA CLARA -- Four pounds has never seemed so significant.
A.J. Jenkins began his rookie season with the 49ers last year at 192 pounds. On the first day of organized team activities this year, Jenkins met the media in a sleeveless shirt to report his weight is up to 196.
"I think I have (added muscle)," Jenkins said before flexing, "You tell me. I might have the guns out a little more this year.
"I was just working my butt off trying to put on some pounds and gain some weight this offseason."
Still, he's another four pounds short of his target weight of 200. It was the biggest knock against him in his rookie year -- that he didn't have the bulk to go across the middle in the NFL. Jenkins was only active for three games and didn't catch a pass in a rookie season he called "very humbling."
Though he is still the lightest among the youngsters competing to be the 49ers' No. 3 receiver, Jenkins enters his second NFL season with a chance to do just that.
"That's my goal."
[MAIOCCO: Wide receiver competition will be fierce]
Jenkins' plus quickness, his ability to stretch a defense vertically and his large hands seemingly put him in a great position to land the gig, but he did more than get bigger this offseason.
"I'm a lot better than I was last year around this time," Jenkins said.
He spent two months this offseason living in a downtown Atlanta condo with quarterback Colin Kaepernick and fellow receiver Ricardo Lockette working out with the playbook every day.
"My knowledge of the game, my speed, route-running ability, working out coverages," said Jenkins, recalling what his believed areas of improvement. "I was trying to get everything better."
The 30th overall pick in the 2012 NFL Draft is already appreciative of having 11-year NFL veteran Anquan Boldin on his side this time around.
"He's got the knowledge down," Jenkins said. "I'm trying to take that part from his game, and put it into mine."
Jenkins will compete with Quinton Patton and Ricardo Lockette for the third-string receiver position, with the injured and more accomplished Mario Manningham and Kyle Williams waiting to provide more competition down the line.
Patton, the team's fourth-round pick this year, stands 6-foot and weighs 204 pounds. Lockette is a 6-foot-2, 211-pound target in his third NFL season, and his size and speed drew rave reviews from head coach Jim Harbaugh at the NFL owners meetings.
[REWIND: Harbaugh 'fired up' about Ricardo Lockette]
"There's just something about him that I'm really fired up about," Harbaugh said in March. "He's got something else to him, too, besides just the analytical size, strength, speed. There's something special there. I just feel it."
"He looked great (in Atlanta)," Jenkins said of his competition. "He's big."
Manninghham, who tore the ACL and PCL in his left knee during the 49ers' blowout loss to the Seahawks last December, is expected to return to action in the middle of August. Williams, the 49ers' No. 3 receiver at the start of last season, will not take part in OTAs, but he is expected to be ready by the beginning of training camp in late July.
There's a lot of talent between Jenkins and a significant role in Greg Roman's offense, but the 23-year-old appears to be handling it just fine.
"No pressure at all," said Jenkins. "For what? It's football."