Johnson is concerned that attempting to play now could have negative repercussions further down the line.
"I could try to go this week, and that could put me out for other games later in the year," Johnson said. "It's not horrible, but I have to be smart about it. I just have to be practical and give it the rest that it needs. The more I pound on it, the more it irritates it."
Johnson was an integral part of the Niners' passing attack in the early going and was the team's leading receiver after three games. But the Niners have gone away from passing to their tight end with Johnson out, and Justin Swift has played adequately is Johnson's place to lessen the impact of not having him in the lineup.
The Niners could be without Johnson for a few more weeks, which is on the long end of the original diagnosis that he might miss from 3-to-6 weeks. Johnson had an epidural shot to relieve stress in a bulging disk last month after his back began flaring up after a Oct. 20 loss to New Orleans. The ailment had bothered Johnson in previous weeks but hadn't been enough to keep him out of games until he aggravated it against New Orleans.
"He's feeling better than last week and he's getting closer," Niners coach Steve Mariucci said. "Hopefully any time in here it will calm down. I can't play him right now without any practice. Right now we're rehabbing him, trying to calm it down, see if it heals and feels better here soon so we have him for the stretch."
Which means the Niners probably won't have him Sunday for San Diego.
"It's not looking too good," Johnson said. "I just need to rest and be good with my rehab. I can't rush it back."