When thinking of the most elusive players in the NFL, Philadelphia Eagles running backs LeSean McCoy and Darren Sproles are right in the middle of the discussion.
McCoy is a player the Washington Redskins have faced several times before, including twice last season, but Sunday will mark the first time the NFL's top overall defense will be tasked with stopping both players.
Take a look back at some of the top sacks in Redskins-Eagles history.
Sometimes, it may be stopping both at once.
"They use them interchangeably," said defensive coordinator Jim Haslett. "They'll replace each other and Sproles will do a lot of things they did with their receivers last year.
"They'll put him in the backfield, motion him out and doing a lot of different things. So you've got to be on top of your game when both of them are in. …You've got your hands full. When two of them are in, it makes it a little bit worse."
While the duo has combined for 250 rushing yards and three touchdowns through the Eagles' first two games of the season, they have been just as deadly in the passing game, combining for 21 catches for 230 receiving yards.
Against the Indianapolis Colts last week, Sproles recorded seven receptions for 152 yards, and many of his passes were caught via screen pass.
With quarterback Nick Foles' ability to both throw it deep with accuracy and dump it off to Sproles and McCoy in the flat, head coach Jay Gruden said that when they churn up big chunks of yardage it can be like "a dagger in your heart."
"They go really fast, they have great drop-back passes and play-action passes and of course the running game," he said. "Then they throw the screens at you – the receiver screens and the halfback screens.
"They do a great job and sometimes defenses play them extremely well, but the big thing is some of those screens when they hit, they hit for gigantic chunks of yards, and that's the one thing we have to guard against.
"We've just got to do a good job and know where they are and do the best we can of pursuing and taking good angles and wrapping up and keeping our eyes open because both those guys are excellent in space with obviously all the moves they make on defensive players."
For defensive lineman Chris Baker, who has slid over to nose tackle from defensive end with Barry Cofield out due to injury, focus will be a key in containing the Philadelphia offense.
"They always run a fast-paced offense in a sense that they get lined up fast," he said. "But it's not typically fast paced in a sense that they get the ball off real quick, because they have to get their calls too. So we've just got to stay focused and not get rattled when communicating."
McCoy and Sproles are extremely dangerous when they're in open space out wide.
Outside linebacker Brian Orakpo said the defense must go into the game with a mindset that they will not succumb to their moves that generate extra yards.
"The way [McCoy] jumps, cutting guys and making guys miss, spinning and stuff of that nature," Orakpo said of McCoy's strengths. "Sproles has the same element as well, so it's going to be a huge challenge for us, but we're very up for the task and we're very confident in what we're bringing to the table, so it's going to be a good game."
Redskins defensive end Jason Hatcher said McCoy reminds him of Pro Football Hall of Famer Barry Sanders.
"It's hard to bring him down because he's so quick," he said. "McCoy reminds a lot of Barry Sanders back in the day. He's got so many characteristics as far as a football player. We've got our work cut out.
The Eagles have won their first two games by wearing down their opponents.
In the season opener against the Jacksonville Jaguars, the Eagles entered the locker room at halftime down 17-0 before registering off 34 unanswered points in the second half.
Against the Colts, the Eagles trailed by as many as 14 points in the second half before hitting a game-winning field goal as time expired.
Much of this can be credited to their up-tempo attack and the running game's ability to extend plays. Outside linebacker Ryan Kerrigan, however, believes the Redskins' defense is properly equipped to keep up with their offense for four quarters.
"We're well conditioned," he said. "It's a fast paced, up-tempo offense to face, but they're human too."