On first-and-10 from the San Francisco 31-yard line, the 49ers lined up Michael Crabtree (red circle) inside of Vernon Davis (yellow circle) in the left slot.
Davis ran a deep route down the seam to clear out the area. The Ravens were in a Cover-3 look, which made it a perfect defense to run the route combination against.
Crabtree ran inside and broke it to the left with a sharp move to get open. He then banged off corner Cary Williams and raced into the end zone for the score.
Colin Kaepernick could have gone inside to Davis, who was also open.