Let's take a look at four crucial breakdown's by the 49ers secondary from Sunday's loss to the Cardinals.
1st Quarter - 3rd and 4, AZ 26, 49ers are in Dime vs 10 personnel for Arizona.
This is the third play of the game. On this play Vic Fangio dials up a blitz for Jimmie Ward from the slot leaving Antoine Bethea one-on-one with Michael Floyd. The blitz doesn't get home because the RB does a good job of coming over to pick up the blitz and Stanton takes advantage of the mismatch between Floyd and Bethea with a perfect throw.
2nd Quarter - 3rd and 8, AZ 17, 49ers are in Dime vs 10 personnel for Arizona.
This is the first Cardinals possession of the second half. The 49ers have them backed up and generate a good pass rush up the field. The problem is they don't maintain their lanes which allows Stanton to step up and throw the deep ball down the left sideline to Michael Floyd who is covered by Chris Culliver. The back end of this play highlights Culliver's inability to turn and find the ball. As he turns to find it, Floyd leaps for the grab.
3rd Quarter - 1st and 10, SF 24, 49ers are in Nickel vs 11 personnel for Arizona.
On this play the 49ers look to be in Cover 3, meaning the corner backs and Eric Reid are each responsible for a deep 1/3 of the field. As the play unfolds Perrish Cox jumps the curl route of the tight end, this is Patrick Willis' responsibility. This allows the wide receiver to be wide open and make the grab in what should be his zone for an easy touchdown.
3rd Quarter - 3rd and 6, SF 21, 49ers are in Nickel vs 11 personnel for Arizona.
On this play Jimmie Ward is playing a trail technique in the slot and is expecting help over the top from Eric Reid. Reid jumps the shallow in route of Larry Fitzgerald, this is Perrish Cox' responsibility, and Ward is left with no chance to make the play.
The two touchdown's are the result of players not playing their own responsibilities. This is an easy fix that requires the players to trust that the man lined up next to them will handle their responsibility.