SANTA CLARA The 49ers' first-team defense Friday was bogged down by all the praise and adoration it has received this offseason.
That's the assessment of defensive coordinator Vic Fangio, who had a funny feeling the defense would underperform Friday against the Minnesota Vikings, then watched the unit do just that.
Behind second-year quarterback Christian Ponder and backup running back Toby Gerhart, the Vikings had two long drives to open the game against a 49ers defense that began the game without only one starter, defensive end Justin Smith. Another starter, linebacker Aldon Smith, was injured midway through the first quarter.
Ponder completed a 52-yard pass on the opening drive, which Fangio called a "busted coverage." Gerhart broke tackle attempts by Ahmad Brooks and Dashon Goldson on a 16-yard run on the second drive.
The 49ers held Minnesota to field goals on both drives and won 17-6, but Fangio knows his unit can play better.
"I think it's a little bit of all the nice things that have been said about them for their play last year," he said. "They started off camp very well, pretty much dominating out here on the practice field, and I just think we got a little full of ourselves."
Gerhart averaged 6.2 yards a carry. That's a big number for a 49ers defense that didn't allow a rushing touchdown until Week 16 last season and held opponents to an average of 77.3 yards on the ground.
Seattle's Marshawn Lynch had the highest per-carry average of any starting running back the 49ers faced last year 5.1 yards in Week 16. He also was the first runner to score a touchdown against San Francisco and was the only one to surpass 100 yards. He had 107.
Fangio said he and some of his assistants suspected there might be a letdown before Friday's game, and he said he wondered at the time if that might be a good thing that a bad outing could refocus the group.
"But while it's happening and even afterward, I don't agree with that, no," he said. "I didn't like looking at it."
Two players come on board The 49ers signed two tight ends Monday because of recent injuries to Delanie Walker and Nate Byham.
Gijon Robinson, who played at Missouri Western, and Joe Sawyer, who played at Southwestern Oklahoma State, attended Monday's practice. To make room on the roster, the 49ers cut guard Garrett Chisolm. The team now is at the 90-man roster limit.
Byham, who is coming back from a torn knee ligament suffered last year, was held out of Friday's game and has not practiced the last two days. Walker suffered a right knee injury in Sunday's practice and did not practice Monday. The injury is not believed to be serious.
Et cetera Defensive starters Brooks, Isaac Sopoaga and Aldon Smith did not practice. Brooks' and Sopoaga's injuries don't appear serious; Smith will miss at least a week with a hip pointer.
Colin Kaepernick completed a pass to Colin Kaepernick. The quarterback's pass was batted back to him at the line of scrimmage. So Kaepernick took off around the left side of the line for a modest gain.
Alex Smith completed long, back-to-back passes down the left sideline to Vernon Davis and Randy Moss. Smith looked sharp throughout the afternoon.