In his postgame press conference, Vikings quarterback Christian Ponder said the Vikings’ success was predicated on their ability to run the ball. 146 yards rushing allowed is certainly an anomaly for a 49ers team that is usually tightfisted on the ground, but it was actually the short passing game that had San Francisco on their heels Sunday.

Ponder has quietly been having a fantastic year, completing passes on 70.1% of his attempts and showing fantastic mobility in the backfield. He stayed efficient against the 49ers on Sunday, spreading the ball around and recognizing holes in the 49ers defense. Much credit is also due to the Vikings’ coaching staff, who found the biggest flaw of them all – Aldon Smith’s inexperience in coverage.

– They attacked Smith early, and went after him almost every chance they got. On a 2nd-and-6 early in the first quarter, they motioned Percy Harvin from right to left and ran him around to the flat once the ball was snapped.

The corner on the left side dropped into coverage and Aldon Smith pinned his ears back to pass rush. The flat was wide open for Harvin, and Ponder could tell immediately that the design had worked.

By the time Harvin caught the pass, there wasn’t a defender within five yards. Smith is off the screen in this shot and far behind the play, which ended with an easy first down for the Vikings. It’s not clear whether Smith was supposed to be covering the flat on that play, but if he was, he didn’t recognize that Harvin was making his way over there.

– Here’s a look at Kyle Rudolph’s touchdown before the ball was snapped. Smith is lined up right on top of Rudolph, who comes off the ball and blocks Smith before releasing into his pattern. Smith doesn’t seem to realize that he has to stick with him.

Rudolph is running free on the right side of this shot. Aldon is standing at the goal line, just realizing that he’s made a mistake. Smith hustled to catch up, but he didn’t get to Rudolph in time. The Vikings’ first six points were on the board.

– The Vikings also took advantage of the 49ers when Smith’s sole responsibility was to rush Ponder in the second quarter. Here is Smith rushing the passer, while running back Toby Gerhart releases out of the backfield completely uncovered.

Gerhart caught the pass for an easy conversion on 3rd-and-2. Nobody was around to stop him.

– In the third quarter, the Vikings looked back to Harvin for a swing pass on the exact same play design we saw earlier. They motioned Harvin across the field and ran a play action fake. Smith made no effort to cover the flat, and it made for more easy yardage.

By dropping the cornerbacks to cover wide receivers, the 49ers left nothing but open space in the flat for Harvin to run. He got the first down and then some on this play, keeping the Vikings drive alive.

– These are just a few examples of how Minnesota capitalized on Smith’s deficiencies, but the Vikings didn’t always take advantage. Here is Kyle Rudolph, who was being well covered by Donte Whitner, on his second touchdown. However, check out Adrian Peterson, who should have been covered by Aldon Smith.

That’s Peterson waving his arm, begging for the ball at the goal line. You can see in the shot that, after initially rushing Ponder, Smith reversed field and tried to drop back into coverage – far too late.

The 49ers are feeling the effects of both the Parys Haralson injury and the decision to make Smith an every down linebacker. This is a problem that they must solve if they want to get their defense off the field and keep points off the board. The flat has become a sieve, and Aldon Smith’s inexperience in coverage is the culprit.