Even if Indianapolis hadn't traded for Trent Richardson on Wednesday, the 49ers still would have a tough time beating the Colts on Sunday.
Look at the facts: The Colts ranked fifth in the NFL in rushing yards without Richardson. They average 5 yards per carry. To beat the 49ers, you have to run the ball well and that's what the Colts do. They probably could have run on the 49ers with the running backs they had already, Ahmad Bradshaw and Donald Brown, but Richardson is better than both of them.
Forty Niners defensive coordinator Vic Fangio gushed about Richardson: "He's strong. He's fast. He's got a good stiff arm. He's a move-the-pile kind of guy, but he's also got some shiftiness too where he can bounce it outside or inside."
Gee, the 49ers could use a running back like that.
Expect Richardson to run on most first and second downs like Marshawn Lynch did Sunday night. And on third downs, expect Andrew Luck to play much better than Russell Wilson did last week.
The 49ers' defense forced Wilson to stay in the pocket and he struggled because he's short. Luck isn't short and doesn't struggle in the pocket. He succeeds in the pocket. Expect Luck and the Colts to convert more than half of their third downs and score at least three touchdowns.
Can the 49ers' offense keep pace?
I don't see how it can.
It's a run-first offense without a running back. Frank Gore's legs aren't coming back. You've seen Gore play this season. Can you picture him breaking out around either end of the formation on a pitch or sweep? Maybe a year ago but not now.
When Gore takes a handoff, the defense doesn't have to worry about him bouncing a run outside because his legs have no bounce and he's slow. If he's going to be effective he has to run up the middle.