The tone was set from the opening defensive drive, and it continued until the final play of the game.
The 49ers defense came to play Sunday in Indianapolis.
The first time the unit took the field, Peyton Manning and the Colts' offense was just 18 yards away from the end zone. But the All-Pro quarterback was forced to settle for just three points.
Four turnovers and one defensive touchdown later, the 49ers proved why it could be among the NFL's best in 2010 as it stifled Indianapolis much of the afternoon in a 37-17 victory.
"I think we played pretty solid, but there is always room for improvement," cornerback Nate Clements said. "It's the first preseason game, so we had an opportunity to see where we stand as far as training camp with all the practices and installation. We had a chance to put it all together today."
Along with its four interceptions, the 49ers defense totaled two sacks, 10 tackles for loss and five quarterback hits. It limited the Colts' offense to just 235 yards, only 58 of which came on the ground.
Reggie Smith was the first to step up.
The third-year safety defended Manning's third-down pass on the opening drive, which forced the early field goal. Then early in the second quarter, he made the play of the game when he intercepted a Curtis Painter pass and returned it 91 yards for the 49ers first score. He stopped the Colts next drive too when he tackled wide receiver Blair White just short of the first-down marker.
Reserve linebackers Keaton Kristick, Bruce Davis and Mike Balogun led the 49ers with six tackles a piece; Balogun also came up with the team's final interception of the game.
"I'm very excited (for the young players)," safety Dashon Goldson said. "When we're at training camp, it's hard to see what you've got because we're not live. The lights are on now and a lot of guys have to prove themselves."
Goldson and most of the 49ers defensive starters came out of the game midway through the Colts' second drive, and later in the possession, Manning marched down the field and put Indianapolis up 10-0.
But the defense didn't quit.
It responded with Smith's pick-six on the next drive and proceeded to hold the Colts scoreless until late in the fourth quarter.
"The guys hung in there and we did some of the things that we needed to do to get back in the game," head coach Mike Singletary said. "I thought we did a good job of running around."
Three of the 49ers interceptions came off of Painter. Two drives after Smith's interception, linebacker Diyral Briggs leaped in front of a Painter pass and hauled it in. However, his effort went for naught as he fumbled the ball back to Indianapolis on the return.
Cornerback Will James accounted for Painter's third interception, which came just before halftime. His takeaway set up a field goal that gave the 49ers a 20-10 lead at the break.
Balogun's fourth-quarter interception came courtesy of third-string quarterback Tom Brandstater
The defense seemed to get stronger as the game went on and closed the game well, but Singletary still isn't satisfied.
He'll take the win, but he knows a lot of progress needs to happen between now and Week 1 for his defense to be where he wants.
"Overall I thought the guys did a pretty decent job and I feel like we're on the right road," Singletary said. "But we have a long way to go."
Rookie Runs Wild
Earlier this week, offensive coordinator Jimmy Raye called Anthony Dixon "a bull in a China cabinet."
Sunday, the rookie running back out of Mississippi State showed what Raye was talking about.
Dixon carried the ball 21 times for 100 yards and scored one touchdown, but it's how physical he ran that most impressed the coaching staff.
"He is young, but obviously shows he has the talent and the strength to do some things," Singletary said. "I thought he made some good strong runs, so that was very good to see."
Dixon was pleased with his first performance in a 49ers uniform, but he knows he's fighting for the No. 2 spot on the depth chart and that he still has a lot to prove.
"I just wanted to go out there and make a statement to everybody that was watching on what type of player I am going to be and what I am going to bring to the field," Dixon said. "I think (Raye) will say it was a good job but I have a lot of work to do. And I do because I made some mistakes today.
"We are going to enjoy this one today, but after this it's back to work."
Dixon entered the game in the 49ers first drive of the second quarter, and he recorded 24 of the team's 43 yards in that touchdown drive.
His touchdown came early in the fourth quarter when he broke two tackles on a 5-yard sweep run to the left side.
Time OffLinebacker Joe Staley, running back Frank Gore, wide receiver Michael Crabtree and kicker Joe Nedney all sat out of Sunday's game.
Singletary said minor injuries played a role in sitting them, but that he also wanted to prevent any new ones.
"I think it worked out, the decisions we made," he said. "I think it will prove to be good going forward."
Injury UpdateTight end Vernon Davis suffered a knee strain near the end of the first quarter.
Defensive tackle Derek Walker suffered a hip contusion, wide receiver Kyle Williams sprained a toe, and James sprained an ankle.