SAN FRANCISCO – The highlight of Sunday's 49ers practice at Candlestick Park may have been the 12th man on the field.

Toward the end of the session, a shirtless, shaggy-haired fan ran from the north end of the field and made his way, amid a roar from the crowd, to where the 49ers were stationed on the south end. His journey ended 2 feet from none other than Jim Harbaugh, who seemed like he wanted to clock the intruder but allowed security to take him away.

"He called me 'coach' or something, but I didn't say anything," Harbaugh said afterward. "Glad he was clothed. Glad he wasn't naked."

Other than that, the 49ers' annual Fan Fest went smoothly. The team reported it had sold approximately 32,000 tickets to the event, four times the number that showed up last year.

That uptick in attendance likely was because of: 1) the high interest and expectations in the 49ers after their 13-3 season last year, and 2) the fact that Sunday's session was the only training camp practice open to the public this year.

In a normal summer, fans can attend one of dozens of open practices at the team's headquarters in Santa Clara. This year, however, 1 1/2 acres of practice fields there were lost to stadium-related construction, which meant there was no room for bleachers or for public practices.

Harbaugh seemed to enjoy the change of pace as he signed autographs for more than a half hour after practice.

"A lot of support for our team," he said of the fans' presence. "I think (the players) felt that from the moment they stepped on the field."

Walker injured – Tight end Delanie Walker went down because of a right knee injury after blocking outside linebacker Eric Bakhtiari in 11-on-11 drills. Walker watched practice with a bag of ice on his right knee before walking into the locker room with a slight limp 30 minutes before the session ended.

Harbaugh said he needed to wait for more information from team doctors but sensed "we dodged another bullet there."

The 49ers already were practicing without tight end Nate Byham, who was held out of Friday's preseason game. The 49ers will try out tight ends this week.

Aldon Smith update – Harbaugh said he thought outside linebacker Aldon Smith would be "out a week … but we'll see."

Smith suffered a right hip pointer in the first quarter of Friday's game and did not return. Parys Haralson will fill in at right outside linebacker while Smith recovers.

Et cetera – Why was Vernon Davis wearing No. 87 instead of his normal No. 85? "I forgot it," he said of his jersey. "In the rush, I forgot it."

• The practice ended with a long, 19-play drive capped by an Alex Smith touchdown pass to tight end Konrad Reuland in the corner of the end zone.

• Defensive end Justin Smith, running back Frank Gore and wide receiver Mario Manningham practiced after being held out of Friday's game. Byham, linebackers Cam Johnson and Darius Fleming, and Aldon Smith did not make the trip to Candlestick.

© Copyright The Sacramento Bee. All rights reserved.

• Read more articles by Matthew Barrows

Order Reprint