That will be no easy task, considering Manning has thrown 25 touchdowns in just seven games. The emergence of tight end Julius Thomas and the arrival of Wes Welker has made Manning even more difficult to contain.
But there are still some things defensive coordinator Jim Haslett can do.
Disciplined deep coverage and taking away the middle
Maintaining a stable deep coverage shell is essential to keeping Manning off balance and forcing mistakes. In particular, there has to be a commitment to taking away the deep middle, especially the seams.
The deep inside is still usually Manning's first and preferred read. Taking this away will force the Broncos to put together lengthy drives and could lead to mistakes.
Looking for examples of teams who have succeeded in this area this season is not easy. In fact, the lowly Jacksonville Jaguars actually came the closest.
When the Broncos beat the Jags 35-19 in Week 6, Manning was held to 295 yards passing and only seven yards per completion. Both are season lows.
A key to their performance was an adherence to Cover 2 concepts that consistently forced Manning to throw short and underneath.
On this play from the second quarter, the Broncos faced 2nd-and-6 at their own 24-yard line. The Jaguars played a standard Cover 2 shell.
Once the ball was snapped, notice how the cornerbacks made initial contact with Manning's wide receivers before passing them off to the deep safeties.
The Jaguars also dropped their three underneath defenders into a flat zone look in the middle. This crowded the inside and took away the hook and curl routes in the seams.
That left Manning with only one viable target, Welker, who was in front of the underneath coverage.
Manning's outside receivers were bracketed by the deep safeties and the defenders in the seams. Meanwhile, his underneath receivers were taken away by the cornerbacks covering the flats.
It was clear how this affected Manning. You can see he was initially looking downfield.
But the deep zone shell and pressure from outside rush end Jason Babin soon forced Manning to look underneath.
Manning threw to Welker, but the coverage in the middle quickly closed in, forcing the pass to fall incomplete.
This was not innovative in a schematic sense. But the Jaguars stayed patient and disciplined to deny Manning the kind of quick-strike big play he often relies on.
This bend-don't-break approach is often necessary against Manning, but it does not mean a defense can't still be aggressive.
That is just what the Jaguars were on one of the game's biggest plays, shortly before halftime.
With the Broncos facing 3rd-and-7 at their own 45, Jacksonville adopted a Cover 2 Man look.
They had both corners rolled up in press coverage on the outside. On the inside, the slot defenders would retreat in off-man coverage.
Two deep safeties would take away the vertical routes behind this underneath man coverage.
Once the ball was snapped, the Jags immediately took away the inside routes while linebacker Paul Posluszny lurked free in the middle.
As the play progressed, the coverage shell was set. Manning's seam receivers were bracketed by man coverage underneath and the deep safeties over the top.
The cornerbacks on the outside pressed their receivers to the sideline and took away the inside breaks.
This disciplined coverage in deep areas left Posluszny free to spy Manning in the middle and read the quarterback's eyes.
Posluszny was therefore in perfect position to snatch Manning's pass to the seam. He would return his theft 59 yards for a touchdown.
On both of these plays the Jaguars committed to a seven-man coverage scheme. That gave them a numbers advantage and they made it count by staying disciplined.
The Jaguars were rewarded for their patient approach. Their coverage was tight and stable and Manning still could not resist eventually trying the deep inside.
The Redskins can easily adopt a similar plan. They used the same zone shells to great effect against the Oakland Raiders in Week 4.
But the key is shifting to their zone drops and staying patient. Covering defenders have to focus only on keeping the ball in front of them and making Manning settle for less.
As good as Manning is, and he may be the greatest to ever play, he has always had a gunslinger mentality. Slowing him down can lead to mistakes.
The more the Redskins frustrate Manning by taking away the kind of quick-strike big plays he loves, the more opportunities they will get to add some aggressive concepts to the game plan.
Risking Man coverage and combination blitzes
Normally, it is an unwritten rule not to risk the blitz against Manning. His quick release and ability to decipher pressure looks pre-snap makes blitzing Manning a very risky proposition.
But it is not impossible for defenses to have success when bringing additional rushers against Manning. The Indianapolis Colts proved that in their 39-33 Week 7 win.
The Colts got plenty of hits on Manning and put themselves in position to risk the blitz. In the fourth quarter, with Manning and the Broncos pinned deep, Indianapolis blitzed the middle.
The Broncos lined up in a formation featuring Thomas and Welker on the same side, a look that has been killing defenses. They brought Thomas across the formation in motion.
With Thomas now aligned as a flex tight end, inside 'backer Jerrell Freeman (50) shifted over into a coverage look. The Broncos wanted the mismatch of a linebacker covering Thomas underneath.
But instead deep safety Antoine Bethea (41) would move from his Cover 2 alignment to take Thomas in man coverage.
That's because the Colts planned to blitz Freeman. He would run a stunt with interior D-lineman Ricky Jean-Francois.
Freeman's blitz lane would be cleared by end Erik Walden taking a wide rush on the outside and Jean-Francois slanting that way.
Freeman and Jean-Francois combined to drop Manning for a seven-yard loss.
Their pressure was aided by tight man coverage underneath and deep. The Colts plastered all five of Manning's targets while a single-high safety lurked over the top.
Indianapolis had used Denver's formation against them by blitzing defenders who would ordinarily have been in coverage. NBC Sports commentator Cris Collinsworth noted that Manning had expected to see Freeman drop out in coverage on Thomas.
The Redskins can risk the same combination coverage and blitzes to thwart Manning and his favorite weapons. Haslett used similar concepts to frustrate the Chicago Bears at times in Week 6.
One critical example came in the fourth quarter, with the Bears driving for a go-ahead touchdown.
The Redskins used a bold pressure front to corral Chicago's three principle offensive weapons.
They planned to double wideout Brandon Marshall in the slot, shown in the yellow circle. That coverage would be combined with a blitz to target tight end Martellus Bennett and running back Matt Forte, shown in blue circles.
Haslett crafted the blitz look by moving his personnel around. Slot corner Josh Wilson (26) joined the line, while outside linebacker Ryan Kerrigan shifted inside to defensive tackle.
On the other side, inside 'backer Perry Riley Jr. (56) aligned on the edge as an outside rusher.
The Redskins forced the Bears to decipher who would rush and who would drop out from this seven-man front.
Wilson and rush end Rob Jackson (50) would be the ones to drop out, while Kerrigan, Barry Cofield, Brian Orakpo and Riley rushed.
Haslett would also supplement the four-man rush with a late blitz from cornerback David Amerson. Riley and Orakpo would help create a lane for the rookie to attack.
Amerson was given time to get to backup quarterback Josh McCown by the coverage behind the pressure.
Notice how Jackson and Wilson had bracketed Marshall, McCown's primary receiver, in the middle. Meanwhile, Bennett and Forte could not release off the line as they were forced to help in pass protection.
Haslett had sent only five, but still effectively occupied seven blockers. Amerson beat Forte and hit McCown, forcing an incomplete pass to make the Bears settle for a field goal.
The Redskins had used a zone pressure to nullify the Bears' biggest offensive threats and still create pressure on the passer. Haslett can use similar schemes to stymie Manning and his stable of playmakers.
He can combine pre-snap movement and complex blitz looks with combinations to take away Thomas and Welker on Manning's favorite routes to the inside.
Imagine this play with the Redskins' zone droppers doubling on Welker in the slot while blitzers prevent Thomas from releasing.
The key will be Haslett using pressure calls like this selectively in Denver. They can only be made possible by disciplined coverage on early downs.
Blitzing Manning obviously carries risks, but one thing is certain, there will be no prizes for keeping the score down against the Broncos.
At 2-4, the Redskins should take a few risks in a game nobody expects them to win.
But they have to use smart gambles and still emphasise taking Thomas and Welker away. Fellow receivers Demaryius Thomas and Eric Decker are both exceptional players, but Welker and Julius Thomas are really making the Broncos so dangerous.
Containing their threat and harassing Manning is the best way to slow down this offense.
If the defense combines patient and structured deep coverage with selective use of pressure, they will frustrate Manning into errors their own prolific offense can capitalize on.
All screen shots courtesy of CBS Sports, Fox Sports, NBC Sports and NFL.com Game Pass.