INDIANAPOLIS — Indianapolis’ 16th straight regular-season victory will fit neatly into the Colts’ record book.

This week’s game tapes will show the Colts how imperfect they really are.

With Peyton Manning out of sync and the offense struggling to score touchdowns Sunday, the Colts turned to a former quarterback — Joseph Addai — for a 22-yard TD pass that gave Indy an 18-14 victory and its own version of a perfect regular season.

“We need these games if we’re going to push toward our goal, which is the Super Bowl,” receiver Reggie Wayne said. “We’re going to need these close games, we’re going to need to fight through a little adversity and push forward. We were able to do that today. It was a grinder. We figured out a way to win.”

Clearly, there’s plenty of work to do after Sunday’s sluggish offensive performance — despite all the accolades.

Jim Caldwell became the first rookie coach since the 1970 merger to win his first seven NFL games. Indy extended its franchise record and became the eighth team in league history with 16 straight wins. The Colts are now the last undefeated team in the AFC again, the fourth time in five years.

But this was not typical Indy.

While Manning finished 31 of 48 for 347 yards, he missed high, wide and even short, failing to match the incredible efficiency he had in Indy’s first six games. The three-time MVP also failed to throw a TD pass for the first time since Nov. 30, 2008, leaving that job to Addai, the high school All-American quarterback.

It was Addai’s first TD pass as a pro and the first by a Colts non-quarterback since Ken Dilger threw one in 2001. The result was perfect: Wayne lunging toward the end line, getting both feet on the ground to give Indy its first lead 7 seconds into the fourth quarter.

Wayne had a career-high 12 catches for 147 yards.

“I was just trying to get the ball out there,” Addai said. “In practice, I’m just kind of spotting up there, kind of looking, reading my keys. I don’t really have a key to read, but I kind of sit back there like a real quarterback.”

For San Francisco (3-4), it was another frustrating day.

The 49ers have now lost three straight despite getting a solid performance from Alex Smith in his first start in nearly two years. Smith was 19 of 32 for 198 yards with one TD and one interception. He was sacked four times behind a makeshift offensive line that may have sustained another devastating blow when left tackle Joe Staley went down on the first play of the game. The 49ers are already without right tackle Tony Pashos for the rest of the season.

Yet thanks to Smith’s steadiness, Frank Gore’s long run and the continual contributions of Vernon Davis and Michael Crabtree, the 49ers controlled the game for most of three quarters.

It was good enough — almost.

“A couple dropped balls make the difference in a game like this,” 49ers coach Mike Singletary said. “Any missed opportunities in a game like this are going to bite you in the end. The only thing I can say is we came here to win the football game.”

The Colts’ defense had to keep Indy in the game after allowing Gore to slip through the middle, break two tackles and sprint 64 yards for a score on San Francisco’s second series. It was the first TD Indy allowed since Week 4. Gore finished with 13 carries for 91 yards and five receptions for 43 yards.

Manning, meanwhile, settled for field goals.

After the Colts closed to 7-6 early in the second quarter, the 49ers answered with Smith’s 8-yard TD pass to Davis with 33 seconds left in the half.

Two problems: They left Manning enough time to move back down the field and Davis’ celebration led to a 15-yard penalty that gave the Colts even better field position.

The Colts took advantage. Manning needed three plays to set up Stover for a 31-yard field goal to make it 14-9 at the half, and then Manning opened the second half by taking the Colts 52 yards for Stover’s fourth field goal of the day.

That’s how it stayed until the Colts pulled out the halfback option.

“I thought we weren’t quite as sharp as we have been at times,” Manning said. “There’s definitely some areas we can improve on.”