NFL games are a series of probabilities—22 loaded dice rolled over and over with each play.
With every roll, the numbers break a little more for one team more than the other—and over the course of the game these small advantages add up to victories.
But late in the game, as things get critical, there's usually a single play that swings the game in favor of one team or the other, a single play that overcomes three quarters of bad breaks or grants the team with the upper hand an even bigger advantage.
Let's break down the five weightiest plays of Week 2 in the NFL.
Detroit Lions at San Francisco 49ers
With 6:41 left in the fourth quarter, the 49ers were facing 3rd-and-14 from their own 27-yard line. If they didn't pull off a shocking conversion, they'd be giving the Lions decent field position and over six minutes to drive and possibly tie the game.
But pull it off they did:
The Lions line up in a 4-2-5 nickel, with linebackers DeAndre Levy and Justin Durant lining up just as deep as all three cornerbacks, about six or seven yards off the ball.
The 49ers are lined up in the shotgun, with trips to the right. Mario Manningham is the split end to the left, and Michael Crabtree is the slot receiver of the trips, between tight end Vernon Davis and flanker Kyle Williams.
At the snap, the linebackers and cornerbacks all backpedal several steps, leaving basically the entire space underneath open. Fortunately for the 49ers, that's exactly where they're attacking the Lions defense.
Davis' route draws the attention of both Levy and Durant, who again are already backpedaling. This leaves Crabtree dragging across the middle of the field and nobody on tailback Frank Gore. With Manningham occupying his man, Durant is the only defender with a chance to make the play. Gore takes Durant out of the play with a truly incredible block.
Crabtree is sprung for the first down.
Instead of getting the ball back with six minutes left, the Lions allow the backbreaking scoring drive to continue. The Lions were right to keep the play in front of them, but they conceded far too much space to two targets (Crabtree and Davis) who are a load to bring down in space.
Credit San Francisco with a good play call, Manningham and Gore with great blocking, and Alex Smith for getting rid of the ball quickly and accurately.
Arizona Cardinals at New England Patriots
The Cardinals were in the midst of shocking the reigning AFC champions, leading 13-9 with 1:17 left in the third quarter. Their four-point lead, though, was hanging by a thread, as they faced a 2nd-and-18 on their own 28.
If they surrendered here, momentum would swing hard towards the heavily favored hosts:
At the snap, the Cardinals are in a similar formation to the 49ers' long-yardage play above: shotgun, trips right. Tight end Todd Heap and flanker Andre Roberts bracket slot receiver Larry Fitzgerald. I believe the split end up top is Early Doucet, though without the end zone camera I can't confirm that.
The Patriots line up in a nickel alignment, with both safeties positioned very deep.
At the snap, things get interesting. All three Cardinals wide receivers go long, with Fitzgerald feinting inside before breaking deep. Heap initially stays in to chip, then wheels into the area Fitzgerald and Roberts vacated.
Up top, tailback Ryan Williams releases into the flat and calls for the ball. Kolb is looking downfield to Doucet, but the Patriots did a great job of disguising coverage: Linebacker Jerod Mayo peeled off to help double-team Doucet.
At the bottom of the screen, the nickel cornerback (can't confirm his number) initially shows man-to-man against Fitzgerald, but peels off to double Roberts along with corner Kyle Arrington. Before Kolb can contemplate this turn of events, Patriots defensive tackle Kyle Love forces the issue.
I have middle linebacker Brandon Spikes flagged with a question mark, as he appears to be playing a sort of short center field. But when Kolb expertly steps up to avoid Love, Spikes sprints all the way up to lay a (late) hit on the quarterback. Steve Gregory also hits Heap late, and the combined play and penalty yardage sustain what becomes the game-winning touchdown drive.
Baltimore Ravens at Philadelphia Eagles
Mike Vick and the Eagles were down by a touchdown with 2:17 left in the game. Facing second down and a long 13 yards to go from the Ravens' 25-yard line, Andy Reid and his staff dialed up a great play.
The Eagles are lined up in an offset I-formation, with tight end Clay Harbor on the left, wide receiver DeSean Jackson split right and slot receiver Jason Avant also lining up to the right. Fullback Stanley Havili is offset to the strong side.
The Ravens are in their base 3-4, with both outside linebackers cheating up to blitz and both inside 'backers ready to drop back in coverage. Both cornerbacks are at the top of the screen, playing man on the receivers, and safety James Ihedigbo is lined up over Harbor.
Watch the inside linebackers if you want to see the power of play-action. The Eagles' offensive line zone blocks to the strong side, and Vick and tailback LeSean McCoy sell the play fake. In unison, the Ravens' inside linebackers take a step toward the play side. Ray Lewis freezes once he sees the play fake, while Jameel McClain rushes up to contain/pursue Vick.
Harbor runs between them, unnoticed, then breaks for the sideline.
Ihedigbo pursues Harbor, but he can't catch up. Ravens DE Arthur Jones breaks through the moving pocket and gets in Vick's face, but Vick has plenty of time to hit the wide-open Harbor. Jones pops Vick well after the ball is gone, tacking on a 15-yard personal foul penalty to the end of the play.
The end result? First-and-goal Eagles, and shortly thereafter the game-winning touchdown.
Minnesota Vikings at Indianapolis Colts
Peyton Manning broke into the NFL with the help of a veteran deep threat: Marvin Harrison. While Reggie Wayne is much more, er, "veteran" now than Harrison was during Manning's rookie season, Andrew Luck is already reaping the benefits of working with a wideout who knows how to get open deep.
With just 14 seconds left before halftime, the Colts had driven down to the Vikings' 30-yard line. Colts kicker Adam Vinatieri was warming up, and Andrew Luck had one chance to get it a bit closer for him... or maybe not.
The Vikings were doing a lot of pre-snap shifting, hoping to confuse the rookie. Here's the first shot we see of the Vikings alignment...
...and at the snap, it looked more like this:
The Vikings rushed only their four down linemen out of a dime package, with E.J. Henderson the sole linebacker. They appear to be playing matchup zones underneath a deep Cover-2 shell. The Colts kept a tight end and tailback Donald Brown in to block.
At the snap, Wayne cuts inside of the dime cornerback, who tries to pass him off to the backpedaling Henderson. It doesn't work, because Colts receiver Kris Adams, lined up next to Wayne, is also wide open;
Vikings safety Mistral Raymond is left trying to cover two wide-open receivers 20 yards apart. I can't confirm which Vikings defensive back was matched up on Adams, but the defender initially let Adams pass as if handing him off to safety help, then furiously tried to recover as he realized the help wasn't there.
Luck saw Wayne flying past Henderson first, though, and delivered a perfect ball.
Washington Redskins at St. Louis Rams
With 1:49 left in the game, the Redskins were driving towards, at worst, the game-tying field goal, and at best a victory-sealing touchdown. On the Rams 36, Robert Griffin III and the 'Skins offense needed eight yards on third down to move the chains into field-goal range.
The Redskins are lined up in shotgun trips, and the Rams are lined up in, uh...what?
The defensive line knows what it's doing, but the rest of the back seven seems to be having an argument when the ball is snapped. The Redskins are attacking the right side of the defense, as tight end Fred Davis runs straight down the seam to clear out defenders. Behind Davis, receivers Joshua Morgan and Santana Moss run side-by-side curls that stop just short of the sticks.
Rams safety Quintin Mikell has been effectively blocked by Fred Davis running into him (as Davis curiously calls for the ball). Griffin quickly delivers the ball to a wide-open Josh Morgan, and Rams cornerback Bradley Fletcher flies in from his deep zone to try and stop Morgan from getting to the sticks.
Morgan, broke, or partially broke, three tackles in the space of just a yard. But it wasn't quite enough; cornerback Cortland Finnegan rode Morgan to the ground.
After that, you may have heard, Finnegan raised his hand in anger and struck out at Morgan. Morgan responded by spiking the ball at him, and the refs responded by flagging Morgan and effectively ending the Redskins' comeback attempt.