The New York Giants comfortable handling of the 49ers on the road in San Francisco, was one of the major upsets of Week 6. The key to Big Blue's comprehensive 26-3 triumph, was a smothering defensive performance.

The 49ers entered the game having scored 79 points in their last two contests, but that didn't stop the G-men from dominating thanks to scheme and athleticism. Here are the three ways the Giants' defense shut down the 49ers.

They Attacked the 49ers' Vaunted Running Game

San Francisco's success is determined by their power running game, which often overwhelms opponents. The Giants chose to attack the run, rather than adopting a read-and-react approach.

The first key was using speed to gain quick penetration and disrupt runs at their source in the backfield. To do this Giants' defensive coordinator Perry Fewell regularly had defensive end Jason Pierre-Paul slide inside to tackle.

Pierre-Paul's length and speed allowed him to quickly split the gaps along the interior of the 49ers' offensive line. The ploy destroyed many of the power runs San Francisco's offense favours.

The 49ers like to pull their guards and have them act as lead blockers for running back Frank Gore on the edge. Pierre-Paul's speed took him quickly through the spaces vacated by pulling linemen and allowed him to chase down plays from behind.

Another smart move from Fewell was to match up with the 49ers' run-heavy personnel sets. One of San Francisco's most devastating run fronts involves two tight ends and one wide receiver and an extra offensive lineman, who acts as a fullback for Gore.

Fewell's answer was simply to introduce a fourth linebacker to the mix, giving his defense a heavy eight-man front. This kept Gore to minimal gains out of this usually prolific personnel grouping.

Right from the start of the game, the Giants showed a willingness to blitz the 49er's run with their linebackers. This slowed Gore's initial movement and confused the blocking schemes in front of him.

Without the run, the 49ers were forced out of their comfort zone and quarterback Alex Smith was put in the unfamiliar position of having to win the game through the air.

Different Defensive Line Combinations Put Smith Under Constant Pressure

Smith's task was made even harder by the different combinations of defensive linemen and alignments the Giants used to create pressure. One of their most effective fronts had Pierre-Paul and Osi Umenyiora deployed as wide ends with hybrid rush linebacker Mathias Kiwanuka lined up inside at defensive tackle.

The fourth linemen, Justin Tuck, acted as a roving, stand-up rusher, free to choose any blitz lane. It was similar to the scheme Big Blue used to harass Aaron Rodgers and the Green Bay Packers in last season's NFC Divisional playoff upset.

Once again this rush front worked to perfection and was chiefly responsible for New York's six sacks. Smith was rarely afforded a clean pocket, or the opportunity to release a pass unmolested.

Combination Coverage Challenged Smith's Accuracy

When Smith was able to attempt a pass, he was challenged to be as precise possible, thanks to some shrewd combination coverage. The Giants utilized a man-under, two-deep concept, meaning the corners played tight press coverage underneath, leaving the safeties deep, free to spy Smith in zone.

Two of New York's three interceptions came thanks to this coverage scheme. Safety Antrel Rolle was particularly dangerous as a backfield spy.

The Giants bet right by gambling that Smith couldn't be accurate enough to combat tight coverage and intense pressure. The 49ers work hard to ensure Smith doesn't have to win a game by himself. Making sure he had to was the real secret of the Giants' defensive success.