The general assumption for Philip Rivers and the Colts heading into their Monday night tilt with the San Francisco 49ers was that the Colts would – just like they had a week prior against the Seattle Seahawks – lean on Jonathan Taylor and the run game.

Those predictions were quickly disproved, though, starting with the Colts' first drive of the game and continuing throughout the rest of the night as Rivers wasn't shy about slinging the ball downfield. He and the Colts offense did their part in the first half, scoring on three of their five possessions, but as the 49ers continued to find ways to carve up a struggling Colts defense, the offense also found themselves faltering as the game went on.

In the end, the lack of complimentary football and loss of momentum did the Colts in as they fell to the 49ers 48-27, losing their fifth straight game and dropping to 8-7.

The Colts offense started emphatically, as Rivers engineered completions of 18, 19 and 20 yards on the first drive alone. His longest completion in last week's game against the Seahawks was 17 yards. Rivers' 20-yard completion was a perfectly placed throw to Alec Pierce for the Colts' first touchdown of the game.

The 49ers answered back quickly, taking full advantage of a porous defense as they marched down the field for a touchdown drive of their own. And after a fumble on the ensuing kick return, quarterback Brock Purdy needed just a few plays to eventually find running back Christian McCaffrey for another touchdown.

On the following Colts possession, Rivers once again put together – with pinpoint accuracy – another scoring drive with completions of 12, 16 and 17 yards. And again, he finished the drive with a touchdown pass to Pierce.

Monday marked Pierce's first career two-touchdown game, and he had both touchdowns with just over 14 minutes remaining in the second quarter.

From there, though, the momentum shifted back to the 49ers as Purdy put together another touchdown drive – this one to tight end George Kittle – to retake a 21-14 lead. The final three possessions before halftime went like this: Colts three-and-out, 49ers field goal, Colts field goal, 49ers missed (64-yard) field goal.

Throughout the first half, the Colts defense was continually attacked both in the air and on the ground by the 49ers, with an ineffective pass rush and a secondary that struggled to keep up with the likes of Kittle and McCaffrey. At halftime, Kittle and McCaffrey combined for 95 of the 49ers' 165 receiving yards, and McCaffrey led both teams with 11 carries for 67 yards.

That trend continued into the second half as the 49ers took the ball out of halftime and drove downfield for yet another touchdown, finding holes all over the field to string together multiple 20+yard passes before a three-yard touchdown pass to extend their lead to 31-17.

The Colts were forced to settle for a field goal on their next possession after two consecutive incomplete passes; Blake Grupe connected from 51 yards on his second field goal attempt of the day.

The 49ers responded with a field goal drive of their own, but as the game entered the fourth quarter Rivers continued to drive the Colts down the field to keep them within range of a fighting chance. He connected with Tyler Warren on back-to-back plays to bring the Colts into the red zone and found Mo Alie-Cox for an eight-yard completion to put the Colts at the one-yard line. Taylor was the one to bring the ball over the line to cut the 49ers lead to 34-27 as he scored his 19th touchdown of the season.

However, Purdy yet again put together a 10-play, 70-yard drive that ended in another McCaffrey touchdown; Monday became the first time the Colts gave up 40 or more points this season.

The Colts went three-and-out, but an interception by Cam Bynum put the ball back in Rivers' hands with four-and-a-half minutes remaining. However, just three plays later, Rivers himself was picked off and the 49ers returned the ball for a pick-six to go up 48-27.

Backup quarterback Riley Leonard entered the game with just under three-and-a-half minutes left and the Colts turned the ball over on downs. The 49ers then ran the clock out to seal the win.