SANTA CLARA, Calif. — Disgusted by a fumble during practice, San Francisco 49ers coach Mike Singletary warned his players that the next player to turn the ball over would be banished from the field.

Happy trails, Alex Smith.
The quarterback threw a hard-luck interception just minutes after Singletary laid down the law Monday. That sent Smith trekking up to the top of Singletary’s hill — the one nicknamed Mount Pain.
Smith had a scenic view as fellow quarterbacks Shaun Hill, Damon Huard and Nate Davis got the action over the next 30 minutes or so.
Considering that Smith’s throw wasn’t that bad, the punishment didn’t fit the crime. Singletary knew as much, and he smiled and greeted Smith with a hearty handshake once the sentence had been served.
Smith smiled, too, because he liked the message Singletary was trying to send.
“You can’t turn the ball over,” Smith said. “That’s the bottom line. That’s the point Coach is trying to make, and it’s the right point. You lose ball games like that.”
On the ill-fated play, Smith tried to throw the ball to tight end Vernon Davis in practice. But the ball was tipped at the line, then by another defender. The ball kept bouncing around like a ping-pong ball in a lottery hopper until cornerback Marcus Hudson snatched it away from the turf.
Smith acknowledged that it was a bit of a freakish play. But he also said there is a lesson there about quarterbacks forcing a throw into coverage. “You can’t throw the ball into town meetings,” he said.
Teammates realized Smith got a raw deal. During a break in the action, his entire starting offensive line came up and sat with Smith on the hill.
—Singletary held back on announcing his quarterback rotation for the Broncos exhibition. He indicated he might even wait until Thursday before making his selection.
—As for the regular-season starter, Singletary said he might not make the pick until after the third exhibition game at Dallas on Aug. 29.
—Mike Nolan, now the Broncos’ defensive coordinator, returns to San Francisco for the game. Nolan went only 18-37 as 49ers coach, but Singletary remains a supporter.
He noted that Nolan took over a terrible roster and a losing culture.
“I saw Mike come in, roll up his sleeves and go to work trying to bring a structure to this organization and trying to bring about a mental toughness, trying to bring about character,” Singletary said. “Mike will always be a great friend.”
—The 49ers recently instituted a three-second clock at practice. A buzzer sounds after three seconds as a reminder that the play ought to be over. It’s a useful tool for the quarterbacks, of course, but Singletary said it also applies to all positions.
Are the offensive linemen holding their blocks? Have the defensive linemen engulfed the quarterback? Have the receivers run an efficient route?
“Offense is a matter of timing and rhythm and trust and all those things,” Singletary said. “That is one of the ways we can develop that.”
—Gore will not play much against the Broncos. The 49ers see no need to expose him to the risk of preseason playing time. Linebacker Patrick Willis (ankle) might not play at all.
—Fullback Moran Norris was excused from practice to attend to a personal matter. There is no timetable for his return.
—Running back Glen Coffee had a light workload because of a sore ankle. Receiver Isaac Bruce was poked in the eye and came off the practice field, but the injury is considered minor.