SANTA CLARA — In unison, offensive linemen Alex Boone, Joe Staley and Adam Snyder stood up from their post-practice ice baths and headed for the locker room to prepare for afternoon meetings.
"Invite only," an always-animated Boone cracked. "You can't just hop into that group. That's a tub club."
And he's not joking.
Seeing them together in a line of individual ice tubs was hardly surprising considering the 49ers' tight-knit O-line and its cast of characters at each position. The Niners return a group that started every game together during last season's run to the Super Bowl, and they're determined to take that success even further.
"It's great. Any time you can have guys returning that you've played next to and you know how they play, you know how they think, it really helps the game speed up," Boone said. "It's a big advantage for us, but at the same time, we kind of have a target on our back right now trying to continue to be the best and moving in that direction."
San Francisco's offensive line made major strides last year, and now there is an even bigger task ahead: protecting Colin Kaepernick from Day 1 in the quarterback's first full season as the starter.
Boone insists the line — and Kaepernick — will draw far more attention now.
Left tackle Joe Staley, left guard Mike Iupati, center Jonathan Goodwin, Boone and right tackle Anthony Davis know their job is to keep Kaepernick safe at all times. It's hardly a small chore, even on their own practice field.
"They're a group that works well together, good size," 49ers defensive coordinator Vic Fangio said. "You can tell that they've played together for an extended period of time. We still do fine against them."
Offensive coordinator Greg Roman realizes he is fortunate he already knows what to expect from all of his linemen day in and day out over the course of an NFL season.
"Any time you can get that continuity, it's a bonus," Roman said Tuesday. "Everything is in front of us. We've got to earn it, every day at practice get better, and we've got a great group to do it with. They're working hard and paying their dues."
NOTES: Receiver Kyle Williams didn't practice Tuesday and fellow wideouts A.J. Jenkins and Kassim Osgood each came off the field with apparent right leg issues. Jenkins had his right hamstring rubbed down. ... The 49ers waived injured LB Darius Fleming, who tore the anterior cruciate ligament in his left knee Sunday after missing his 2012 rookie season with the same injury. San Francisco filled the void by signing LB Travis Johnson to a three-year contract.