SANTA CLARA, Calif. —Vernon Davis found out in a hurry that his old antics won't be tolerated with Mike Singletary running the San Francisco 49ers' show.

As if Davis needed a reminder.

After the testy tight end scuffled — he won't call it a fight, rather just an act of being competitive — with linebacker Marques Harris during a recent practice, everybody paid. As in all the Niners running enough "gassers," 12 sprints across the width of the field, to make one pass out as Davis so put it.

"A few guys were mad, but like I told them, 'You can't get mad because there will be times you make the rest of us run,'" Davis said. "I told them they should be happy that I made them run because it's extra work for us and a chance for us to get better, keep our lungs going."

The excitable Davis, a regular fighter during his first three NFL seasons, received a talking-to from Singletary. Star running back Frank Gore spoke up as well. The two have an amicable relationship.

"I wasn't mad about having to run gassers," Gore said Saturday. "I just feel it's his fourth year now, and I told him it shouldn't be him now. Everybody makes mistakes but it shouldn't be him. OK, a rookie, I accept that. It's his fourth year now, now it's time. It's time to be a man and try to do everything right. There are younger guys who probably look up to you on the team."

All this after Davis said before training camp began that he agreed with Singletary's no-fighting rules and that he was beyond such behavior. All this after Davis' infamous early exit against Seattle last season on Singletary's orders — because the then-interim coach disapproved of how Davis responded to him following a personal-foul penalty. It was Singletary's debut after taking over from the fired Mike Nolan.

"I'd rather play with 10 people and just get penalized all the way until we have to do something else rather than play with 11 when I know that right now that person is not sold out to be a part of this team," Singletary said at the time. "It is more about them than it is about the team. Cannot play with them, cannot win with them, cannot coach with them. Can't do it. I want winners. I want people that want to win."

Two years ago, Davis tangled almost daily at training camp and once even went after one of his offensive teammates.

Davis said that Harris, the outside linebacker responsible for covering tight ends, held his jersey during Thursday's first practice. The two had to be separated.

"He held my jersey and I couldn't get off of it, so I swiped his hands out the way and he came up and pushed me," Davis said. "With me being competitive, I reacted back to it. ...

"Sometimes it's bound to happen, but that's not what Singletary wants. He wants us to just let it go and move on because you get in a game situation and something like that goes down, boom, I'm out of the game."

Whether he's finally learned a lesson is anybody's guess. Volatile Vernon himself seems like he wants to cool his jets.

"It's a fine line. It's football and there's a lot of competitiveness," receiver Arnaz Battle said. "Coach Singletary has instilled he wants us to be a family and he wants us to be together and not fight. He wants us to resolve conflicts as men. Vernon, it's his fourth year and he's learned a lot and come a long way. He's continued to mature and he's on the right track."

The 25-year-old Davis, the 49ers' first-round draft pick in 2006, was a Pro Bowl alternate last season after making 31 receptions for 358 yards and two touchdowns in former offensive coordinator Mike Martz's receiver-friendly spread offense. His catches ranked third on the team.

Davis hopes to be utilized more regularly under new offensive coordinator Jimmy Raye, who while in Kansas City kept All-Pro tight end Tony Gonzalez a main part of the Chiefs' mix.

"The way we play offensively has always been tight-end friendly," Raye said. "At the places I've been, the tight end is really an integral part of what we do. His speed and athleticism and his ability to inline block is unusual for a tight end. As a combination of that and his ability to run down field and match up and catch the ball, I see him being very good for us."

That is, if Davis can keep his cool.