SANTA CLARA Tight end Vernon Davis has been cleared by an independent neurologist after his Sunday concussion and was back on the practice field Thursday.
Davis went through the non-contact portion of practice, one of the stages in the NFL's post-concussion protocol. He also has been cleared by a team physician, Dr. Daniel Garza, and passed the so-called exertion test in which a player must be asymptomatic after vigorous exercise. To receive full clearance, the tight end must pass a simulated contact test, which the 49ers likely will administer today or Saturday.
Davis suffered the concussion when he received a jarring hit from Seattle Seahawks safety Kam Chancellor in the first quarter last Sunday.
Davis hasn't missed a start since 2007. He suffered a knee injury on a low hit by Pittsburgh Steelers safety Troy Polamalu in Week 3 that year and missed the next two games.
If Davis can't play against the Arizona Cardinals on Sunday, Delanie Walker and undrafted rookie Garrett Celek would step in as his replacements. Walker would take over Davis' role in single-tight end formations; Celek would fill Davis' role when two tight ends are on the field.
Walker, who is scheduled to become a free agent after the season, has been more involved in the passing game since Colin Kaepernick took over as the starting quarterback.
After Davis went out of Sunday's game, Kaepernick targeted Walker seven times and the tight end caught a season-high four passes for 54 yards and a touchdown.
"My job every week is to go out and prove to teams that I can play and be the No. 1 tight end," Walker said. "With Vernon down, that's just giving me more opportunities to get the ball. If (Davis is out), I might get more passes thrown my way."
Injuries Linebacker Tavares Gooden missed Wednesday's practice because of an illness but was back on a limited basis Thursday. Center Jonathan Goodwin whose locker is close to Gooden's was sick Thursday and sat out the practice.
Also limited Thursday: cornerbacks Tarell Brown (shoulder, knee) and Carlos Rogers (knee, toe); outside linebackers Aldon Smith (shoulder), Ahmad Brooks (shoulder) and Clark Haggans (shoulder); defensive lineman Will Tukuafu (neck); and fullback Bruce Miller (shoulder).