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By ANTONIO GONZALEZ

AP Sports Writer

SANTA CLARA, Calif. (AP) - Hitting and tackling is not allowed during team drills for the San Francisco 49ers, so Eric Reid practices proper technique by driving his body through a makeshift punching bag with the other defensive backs.

Apparently, Reid still needs to hit the bag some more.

San Francisco's first-round pick made six tackles in an impressive preseason debut against the Denver Broncos last Thursday night, including a pair of highlight-reel hits. Whether Reid will be ready to start at free safety against Aaron Rodgers and the Green Bay Packers in the regular-season opener Sept. 8 is still unclear.

``He showed progress. He showed promise,'' defensive coordinator Vic Fangio said Tuesday.

Fangio said he's not sure if Reid will make his first start in Friday's exhibition at Kansas City. For all the potent potential Reid has displayed so far, he's still a rookie - and prone to making rookie mistakes - so the 49ers are trying to ease his transition to the NFL before making him the last line of defense.

Reid, the former LSU standout San Francisco traded up 13 spots in the draft to take at No. 18, said he felt positive about his performance - not giving up a big play and, for the most of part, not missing any tackles. He said starting has been his goal since coming to the 49ers, but ``I try not to look too far ahead.''

I try to look at myself to get better as a player,'' he said.When the coach decides on who's the starter, whether it's me or another guy, I'm going to try to help this team out any way I can.''

While Reid is the kind of big hitter San Francisco is looking for to replace All-Pro safety Dashon Goldson, he's still learning to strike a balance with his aggressiveness.

Reid made a jarring hit on Broncos tight end Virgil Green in the second quarter, but he arrived too late, allowing Green to make the catch for 13 yards and a first down. The rookie's most memorable played came in the third quarter, when Reid raced in from his free safety spot to knock Kemonte Bateman off his feet.

The hard hit whipped teammates into a frenzy on the sideline. But again, the play went for 16 yards and another first down.

The concern from coaches is that such hits could come so late they could draw penalties. Those ball-hawking skills take time to hone in the NFL, where plays develop at lightning-quick speeds.

We love the big hit and coach it and try and get it at any time. He's just got to be smart and know not to hit after the whistle, know not to hit a guy in the head, a defenseless receiver,'' Fangio said.He didn't really have any of those plays the other day. We're going to be as aggressive as we can and as physical as we can within the rules.''

Veteran strong safety Donte Whitner has been helping Reid adjust. He believes the rookie has all the natural ability and intelligence to become an NFL starter.

It's going to take a little experience,'' Whitner said.He's going to take some lumps. He'll have to give up some passes and understand where he's supposed to be. But, hopefully, he comes along really fast. He's making plays on the football.''

The competition to replace Goldson - who signed a free agent deal with the Tampa Bay Buccaneers this offseason - has been among the closest in camp. C.J. Spillman, Trenton Robinson and Craig Dahl all have spent time starting in practice, though Reid has started to emerge as a real possibility to start in Week 1.

Dahl played the opening minutes against Denver, but Reid got the majority of playing time, albeit against mostly second-stringers. That progress has slowed since because Reid sat out practices Saturday and Sunday with a stiff back, which he saw a chiropractor for Monday to get back on the field.

``I didn't know my spine could pop that much,'' Reid quipped.

The 6-foot-1, 213-pound Reid said comprehending the more advanced schemes in the NFL remains his toughest task. He's also adjusting to a 3-4 scheme after playing a 4-3 alignment in college, and while the concepts are the same for a safety, he said his responsibilities can change - often after the ball is snapped.

Reid said his timing will improve - he just needs to keep learning and be patient.

``A coach told me a long time ago,'' Reid said, `"You don't necessarily look for the big hit. It will come to you.'''

NOTES: Safeties Michael Thomas and C.J. Spillman got into a fight following a play during the evening practice. It was unclear what started the skirmish, but 49ers coach Jim Harbaugh dove into a pile of players and broke it up quickly. Spillman, who emerged with his left pant leg shredded, was sent to the locker room. Thomas continued to practice. ... Fangio said he doesn't expect his two injured rookie defensive linemen, second-round pick Tank Carradine (knee) and fifth-round pick Quinton Dial (toe), to return to practice anytime soon. He also said it's possible both will be on the non-football injury list to start the season. ... Former British Olympic discus thrower Lawrence Okoye, a 6-foot-6, 304-pounder trying to make the transition to defensive lineman, played six snaps in the preseason opener. The 49ers are being patient with Okoye but hoping to give him more playing time in upcoming exhibitions. He is making slight improvements,'' Fangio said.And, in his case, slight is big.''

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