Coaches send in signals from the sidelines with every play of an NFL game, but the gesture that gets the 22 players on the field and the fans literally on their toes is the one where he simply flashes two fingers. Hold the kicker. Go for the extra points. Plural.

The Chargers have lost a game and -- just last Sunday -- won a contest because of the outcome of a two-point conversion attempt. Conceivably, the AFC West title could be decided by those two passes, the one the Denver Broncos completed for a 39-38 victory over San Diego and/or the one the Kansas City Chiefs didn't complete in a 20-19 win by the Chargers.

"I'd much rather it be a blowout win," said Chargers defensive lineman Ryon Bingham, "but, yeah, the two-point play at the end of a game does make things more intense. More fun, too ... when you win."

Quite by coincidence, the Chargers are about to play two straight games against teams with players you have to cover like a glove anyway, but especially when it comes to two-point conversion plays. Premier wide receivers Hines Ward of the Pittsburgh Steelers and Marvin Harrison of the Indianapolis Colts are two of the three active leaders -- the other is Baltimore Ravens tight end Todd Heap -- in two-point scores with five apiece.

Moreover, the Colts and Chargers (and Cleveland Browns ) are the NFL's best in two-point efficiency this season, each successful on their two attempts. The Chargers used a conversion pass from Philip Rivers to Darren Sproles for an 18-15 lead in the fourth quarter at Oakland. And, immediately after Sproles' 66-yard TD reception put the Chargers ahead 36-31 at Denver, Rivers hit Legedu Naanee for a deuce.

Of course, that just set up Denver for what's still considered by many the most dramatic finish to an NFL game in 2008, the two-point call by Broncos coach Mike Shanahan that could have come off as either courageous or idiotic. Nearly two months later, Eddie Royal's catch of Jay Cutler's two-point pass remains the difference between division-leading Denver and San Diego in the AFC West standings.

The decision whether to go for the PAT kick or the two is usually a simple case of doing the math. There's actually a chart -- called "The Chart" -- that coaches refer to for advice on whether to kick or go for two when leading or trailing by a certain number of points.

However, Shanahan and Chiefs coach Herm Edwards eschewed a near-certain tie inside the final 25 seconds to put everything on the line. Thus, each avoided the risk of entering overtime with the 50-50 possibility of the Chargers getting the ball by virtue of a coin toss.

Just less than even are the overall odds that a two-point attempt will work. Since the two-point conversion was adopted in 1994, NFL teams have succeeded on 545-of-1,221 tries, a rate of 44.6 percent. The number of attempts has decreased over the past five-plus seasons, with an efficiency high of .512 (21-of-41) in 2006. Seventeen of 41 attempts (.415) this season have been good.

With Rivers at quarterback, the Chargers are 3-for-5. They're 2-for-4 under coach Norv Turner, who also calls all offensive plays and is not a gambling man by nature.

"I think the biggest thing is that you have to understand your Football team," Turner said. "You know what the defense has done in those situations when you are going for two. You know what plays you feel good about, that you can execute. Then you weigh it against the percentages of getting into an overtime game ...

"I'm sure Herm felt that we had moved the ball in the second half and that if they had lost the (pre-overtime) coin toss, that it might not go his way. Put it down to one play. Maybe their record has something to do with it.

"When we played Denver and they made that decision, I think it was based on two things -- they were confident in the play they had and they felt if we got the ball first in overtime, there was a good chance we would score."

By now, chances are pretty good that if a team opts to go for two, the play will be a pass of some kind. Just as the Chargers opted to throw the ball for their two deuces, so did the Broncos and Chiefs against San Diego.

Indeed, 33 of the 41 two-point attempts this season have been passes, including 10-of-11 over the past two weeks. None of the five tries over the past weekend, including one by the Arizona Cardinals on Monday night, was a running play.

"On the run, it's like everybody knows it's coming," said Chargers linebacker Jyles Tucker. "The two-point conversions this year, at least the ones I've seen, are all passes. They're either play-action or spread. That's primarily everything you see in that situation. That's what we saw done to us."

Playbooks, like operating space, tend to shrink immensely when you get the ball on the 2-yard line and only one snap. Rivers said each game plan generally includes just "two or three" plays for two-point attempts.

"But how could you ever pick one?" Rivers said. "It can be tough. Certainly, it's a lot easier to kick the extra point."

Just not nearly as interesting. Or gutsy.

MIXED SUCCESS

A year-by-year look at how NFL teams have fared on two-point conversions:

Year ; Att. ; Conv. ; Pct.

1994 ; 116 ; 59 ; .509

1995 ; 104 ; 40 ; .385

1996 ; 92 ; 44 ; .478

1997 ; 109 ; 47 ; .431

1998 ; 105 ; 41 ; .390

1999 ; 84 ; 31 ; .369

2000 ; 85 ; 35 ; .412

2001 ; 90 ; 40 ; .444

2002 ; 98 ; 47 ; .480

2003 ; 66 ; 29 ; .439

2004 ; 76 ; 37 ; .487

2005 ; 53 ; 27 ; .509

2006 ; 41 ; 21 ; .512

2007 ; 61 ; 30 ; .492

2008 ; 41 ; 17 ; .415

Totals ; 1,221 ; 545 ; .446