SANTA CLARA, Calif. (AP) -- It was another opportunistic, rise-to-the-occasion performance by the San Francisco 49ers' defense against a top NFC opponent in the season opener.
Except for one thing.
''As a group, we weren't pleased with our tackling,'' coach Jim Harbaugh said. ''It's not what we've been accustomed to the last couple of years with our defense.''
The 49ers uncharacteristically missed several tackles in key situations, allowing the Green Bay Packers to turn short gains into big plays before San Francisco pulled out a 34-28 victory.
That's one area where the 49ers will look to get better entering Sunday night's showdown against a top NFC opponent that ran over and through the San Francisco defense the last time the divisional rivals met.
The Seahawks present a different set of challenges for the 49ers with aggressive running back Marshawn Lynch and versatile quarterback Russell Wilson.
Both players gave the 49ers fits when they met late last December at noisy CenturyLink Field.
Lynch rushed for 111 yards and scored two touchdowns while Wilson eluded and frustrated San Francisco's defense all evening. Wilson finished with four touchdown passes and 29 yards rushing as the Seahawks routed San Francisco 42-13, the worst loss of Harbaugh's first two seasons with the team.
''You have the added challenge of defending the plays Wilson creates with his feet,'' 49ers defensive coordinator Vic Fangio said. ''(Lynch) runs the ball extremely hard and is obviously a very hard guy to tackle. Then, just as critical, in last week's game we missed a lot of tackles on receivers. We've got to be able to tackle these guys after the catch.''
Rookie safety Eric Reid, in his first NFL start, missed an open-field tackle near the line of scrimmage that receiver Jordy Nelson turned into a 22-yard gain after the catch. On Green Bay's next possession, cornerback Perrish Cox bounced off tight end Jermichael Finley, allowing Finley to score on a 12-yard catch and run that left the game tied 14-14 at halftime.
There were other blown tackle attempts by a defense that otherwise played well against Green Bay's high-powered attack.
Those could become costly Sunday against a more-balanced Seattle offense that once again will look to establish a ground game against one of the NFL's best rushing defenses. Lynch has three consecutive 100-yard rushing games against the 49ers.
''We don't want to give up anything,'' linebacker Patrick Willis said. ''We don't want to give up 100 yards rushing; we don't want to give up 20 yards rushing. We know we have to get after them, and when you get your shot, you have to make sure and make it count.''
One thing will be much different about the defense that was bruised in Seattle last December: It will have All-Pro defensive tackle Justin Smith, who missed that game after tearing his left triceps during a win over New England the week before.
With a healthy Smith again causing disruption in the trenches, the 49ers are confident they'll be better prepared this time.
''Justin's one of the best defensive players in this game,'' Willis said. ''Any time he's not out there, we miss him. No question about it. We've got him back now, so we know he's going to be a difference-maker, as always.''
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