Redskins defensive coordinator Jim Haslett, left, talks with linbacker Brian Orakpo. (John McDonnell/The Washington Post)

The number of elements to consider, on every third down, run through Jim Haslett’s mind. What protection is the opponent likely to call?

Can Haslett’s Washington Redskins defense get to the quarterback by rushing the standard four players and dropping the other seven into pass coverage? Will he need five — which the Redskins refer to as a “dog”? Or will he send six or seven or — gulp — even eight players, with hopes of outnumbering the blockers and overwhelming the quarterback, all while putting pressure on his lonely cornerbacks to hold up?

“It’s high-risk, high-reward,” said inside linebacker London Fletcher.

The risk was apparent Monday night, when Haslett dialed up a “zero” blitz against Dallas — sending everyone but three cornerbacks — on a third-and-21 play in a game the Redskins led by a point late in the fourth quarter. The result — Cowboys quarterback Tony Romo sidestepping the rush and completing a 30-yard pass to Dez Bryant, covered one-on-one — was the seminal play in Washington’s 18-16 loss.

But for Haslett, that call was just one of many made in a game in which he thought his defense played spectacularly, holding Dallas without a touchdown. The very same max blitz Haslett called on that play resulted, earlier in the night, in an interception by cornerback Kevin Barnes and a forced fumble from safety LaRon Landry. Two weeks earlier, it had resulted in a tipped pass for outside linebacker Ryan Kerrigan, a play Kerrigan turned into a touchdown. In fact, Haslett said in his first remarks since the Dallas game, he had called the defense nine times in the season’s first three games before the third-and-21 play.

“We won nine of them and lost one,” he said. “It’s a great defense. It really is.”

So Haslett is spending this week, as the Redskins (2-1) prepare for Sunday’s game at St. Louis (0-3), sounding completely comfortable with his live-by-the-sword-die-by-the-sword approach to blitzing.

“Would you take it back? Of course you would,” Haslett said. “Coaches always second-guess themselves. It’s still a great defense.”

Though the Redskins have spent a great deal of time discussing the third-and-21 play this week — in part because cornerback DeAngelo Hall ripped into Haslett’s call immediately after the game, to which Haslett said Thursday, “That doesn’t bother me” — much more goes into developing a philosophy of when to blitz and when to cover during the week. “It’s a process,” Haslett said. “We mix it up.”

Haslett believes the success of his blitz-calling shows up in the Redskins’ third-down numbers. Last year, when the Redskins were adjusting to the 3-4 scheme and had some ill-fitting personnel, they ranked eighth in the NFL, allowing opponents a 35 percent conversion rate on third down. Through the first three weeks this year, that number has fallen to 21.9 percent, tied with the New York Jets for best in the NFL.

“We got an idea going into the game exactly what we want to do,” Haslett said, “and then we adjust it accordingly to what they’re doing.”

The mix, coaches say, is one key element of whether blitzes are successful. On the Cowboys’ final drive, Haslett called the zero blitz on both first and second down — plays that resulted in a fumbled snap and an incomplete pass. He then came back with the same call again, which Hall called “unorthodox.” Whatever keeps the offense off-balance.

“You do it based on a lot of things — film study, the situation, what kind of success you’re having,” Rams Coach Steve Spagnuolo said. “You’ve got to pick and choose. . . . A good mixture is what it takes, and whatever is called, if you can get guys to execute it, usually it works out pretty good.”

That, players said, is paramount. Wednesday, Hall spent more than 10 minutes explaining his errors on the play — briefly taking his eyes off Bryant, taking an improper route — and apologizing for a profanity-laced outburst after the game. The message: Players’ performance is more important than any call.

“The thing is, whatever the call is made, us as players we have to execute it and get the play stopped,” Fletcher said. “It’s on us as pass rushers to get to the quarterback. . . . That defense has been excellent for us all season long. We have to go out and execute the call regardless. Any call that’s made, we have to execute it.”

The next opportunity for execution will be Sunday against St. Louis, which is struggling in such situations. The Rams have allowed 12 sacks, fourth most in the league, and their third-down conversion rate of 25.6 percent is worse than all but one team. But regardless of the opponent, Haslett’s position on the sideline will be the same: Deciding when to send his guys, and when to hold back.

“It’s not like a blitz-fest,” Haslett said. “It’s a good mixture of what we do.”