The Indianapolis Colts didn’t expect their return home to be easy Sunday, certainly not as comfortable as things had been in the last month.

How right they were.

On a day QB Peyton Manning referred to as “a grinder,” the Colts trailed for three quarters and struggled at times offensively. But Manning said what was important Sunday wasn’t appearance, but that the unbeaten, AFC South-leading Colts found a way to win, rallying for an 18-14 victory over the San Francisco 49ers in front of 66,299 at Lucas Oil Stadium in downtown Indianapolis.

“It was one of those days,” said Manning, who completed 31 of 48 passes for 347 yards – his sixth 300-plus-yard game in seven games this season – and no touchdowns with no interceptions.

“We kind of call it a grinder, where you keep kind of grinding it out, and fortunately our defense kept them from scoring a lot. We were able to keep the game close. . . .

“There wasn’t a whole lot of offensive rhythm out there. It was just kind of a grind.”

The Colts, who played four of the first six games on the road and who last played at home on the first week of October, had won four consecutive games by double-digits.

On Sunday, they never led by more than four and didn’t lead until the fourth quarter.

“We kind of had a feeling coming into it,” Colts TE Dallas Clark said. “You had a feel that this was a team that keeps it close. Their defense gives them chances for their offense to win it at the end. . . . We were able to kind of play with them.

“It was a grind. It took all four quarters to finally get it going.”

The Colts, who trailed at halftime for the first time this season, cut a five-point deficit 14-12 after the third period. They took their first lead on the first play of the final quarter, with RB Joseph Addai throwing a 22-yard touchdown pass to WR Reggie Wayne.

A two-point conversion pass failed, and the closest the 49ers came to scoring the rest of the game was on the ensuing series. The 49ers drove to the Indianapolis 35, but defensive end Robert Mathis sacked 49ers quarterback Alex Smith for an eight-yard loss that took San Francisco out of field-goal range.

The 49ers failed to move past their 30 on their final possession.

“Our defense sort of rose to the occasion when we needed it most,” said Colts Head Coach Jim Caldwell, who became the first first-year head coach in NFL history to start 7-0.

“The most important thing for us is the next game,” Caldwell said, adding of Sunday’s game, “It was a tight, tough game, but you find a way to win it. Our guys hung in there, came through and made some big plays. They certainly performed well down the stretch.”

With the victory, the Colts extended their franchise-record regular-season winning streak to 16 games, becoming the eighth team in NFL history with a streak that long. New England holds the record with 21 consecutive victories from 2006-2008.

Only three teams have won 17 or more consecutive regular-season games.€

The Colts also remained one of two unbeaten teams in the NFL, and the only unbeaten team in the AFC. The Denver Broncos lost for the first time this season Sunday, 30-7, to the Baltimore Ravens. The New Orleans Saints are unbeaten in the NFC and play Atlanta Monday.

The Colts also remained two-and-a-half game over Houston (5-3) in the AFC South. The Texans have won their last three games, including a 31-10 victory Sunday at Buffalo.

The Colts will play host to the Texans Sunday.

The Colts also extended their NFL-record streak of winning at least seven consecutive games in six consecutive seasons. They have done so each season since 2004.

This is the fourth time in five seasons they have started the season 7-0. They started 13-0 in 2005, 9-0 in 2006 and 7-0 in 2007, winning the AFC South title in each of those seasons.

“San Francisco did a good job on defense, and obviously we weren’t as sharp as we have been at times,” Manning said. “There are definitely some areas we can improve on, but I thought we hung in there, kept fighting and made a couple of third-down conversions where we needed to and scored enough points to win.”