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In a 43-21 rout by the New England Patriots, the Denver Broncos had issues on offense, defense and special teams. It’s not often that a team as good as the Broncos loses, and it’s hard to point the finger at one particular unit as to why.

Although it was a team loss if there ever were one, the most concerning performance was that of a defense that came into the game as one of the best in the league—ranked sixth in points per game allowed through Week 8.

That wasn’t supposed to happen in 2014 because the defense added several key pieces in the offseason. The defense was supposed to pick up the offense if it struggled for a half.

It’s easy to blame the players because they’re the ones on the field, but the defensive struggles Sunday had a lot to do with poor coaching. Defensive coordinator Jack Del Rio had extra time to prepare for the Patriots and somehow came up with an awful game plan.

"They played better than we did," head coach John Fox said after the game via Mark Kiszla of The Denver Post. "And they coached better."

When a head coach admits that the opposing team coached better after the game, it’s a safe bet he’s talking about how they planned and called plays. Offensive coordinator Adam Gase has quarterback Peyton Manning to help him, but Del Rio has no such player on his defense.

It doesn’t absolve players of their poor performances, but it can help explain why players like cornerback Aqib Talib and safety T.J. Ward didn’t play well on Sunday. An ugly early showing by the offense and special teams, a bad defensive game plan and struggles getting pressure on quarterback Tom Brady made things difficult on the defense—particularly in the secondary.

Del Rio’s plan entailed a lot of Cover 3 zone coverage, which would bring Ward down into the box to cover tight end Rob Gronkowski and to make tackles on Julian Edelman. This also entailed playing Talib in off coverage instead of up on the line where he can be physical, the latter of which is his strength. It also meant Ward covering any receivers that happened to be running routes underneath Talib’s zone, which is not his strength.

Not content with the extra defender underneath, Del Rio also decided he was only going to rush three or four. As a result, Brady had a lot of time to pick apart defenders that had little chance to stick with his more agile receivers.

Miller and Ware in Coverage? Spilts Snaps in Coverage % of snaps in coverage Miller vs. Patriots 15 19.00% Games 1-7 Average 6.3 11.10% Ware vs. Patriots 5 8.10% Games 1-7 Average 0.6 1.20% ProFootballFocus.com

Rushing three means that one of linebacker Von Miller or defensive end DeMarcus Ware would either not be on the field or would be dropping into coverage. According to Pro Football Focus (subscription required), Miller dropped into pass coverage 15 times Sunday, three more than at any point this season and nine more than his average. Ware dropped into coverage five times, one more than he had dropped into coverage in the first seven games combined.

With little pressure on Brady on key downs, he was able to find open receivers after they had made a second move. The lack of pressure on Brady put the pressure on Talib and Ward, and they weren’t up to the task.

According to Pro Football Focus, Brady has completed 71.4 percent of his passes for 1,970 yards, 19 touchdowns, two interceptions and 7.9 yards per attempt this season when not under pressure. Under pressure, he has completed just 43.7 percent for 421 yards, three touchdowns and 4.8 yards per attempt.

Brady is great against the blitz, but the Broncos had little chance to get pressure rushing only three players. Del Rio also had Ware and Miller stunting inside a lot, which negated their strength rushing on the outside. It worked in previous weeks, but the Patriots prepared for the maneuver.

Here’s an example of the Broncos rushing four and getting no pressure on 3rd-and-10 early in the game. The Patriots have seven blockers for those four rushers, and the result is an incomplete pass and a punt back to the Broncos. In this case, the Broncos were just lucky the Patriots kept so many guys in to protect.

NFL GameRewind

Poor field position hurt the Broncos Sunday almost as much as big plays. The Patriots scored only once in the first half when the drive started inside their own 40, but the backbreaking drive was probably the last one of the first half, down 20-7 after the offense failed to convert on 4th-and-6.

With just two minutes left, the Patriots marched 57 yards on nine plays for the touchdown to take a 27-7 lead going into halftime. The biggest play on that drive was a 2nd-and-21 that the Patriots converted on a 26-yard catch by Edelman.

NFL GameRewind

Ward was in coverage as Talib’s job was to stay over the top, but Brady stepped away from the pressure by Miller and had plenty of time after that to deliver the ball. From snap to throw was over 4.5 seconds, and Brady had even more time if he needed it. The Broncos rushed three and only Malik Jackson got any pressure, but Brady stepped up away from it and delivered a strike down the field for the first down.

NFL GameRewind

Ward had outside leverage and had to chase Edelman on the outside breaking route, but he reversed course and was wide open for the first down in Broncos territory. Talib seemingly got lost deep in the zone covering grass.

With the Broncos down 27-13 in the third quarter, the Patriots converted on 3rd-and-8 on a 21-yard catch by Danny Amendola. Brady eluded Miller's rush but was otherwise not pressured.

NFL GameRewind

The extra time enabled Amendola to break away from Talib by cutting outside and then back inside. Perhaps the Patriots knew from his time with them that Talib would struggle to plant his left foot once he started moving in one direction.

Later in the game, Brandon LaFell ran outside and then pivoted back to the inside for a first down. For smart receivers on the same page with their quarterback, these whip or pivot routes are hard to cover. They are nearly impossible to cover when the quarterback also has so much time to throw. Talib is the type of cornerback that is particularly vulnerable to such routes.

NFL GameRewind

In the red zone, the Broncos struggled mostly because they were worried about Gronkowksi. With 10 seconds left in the first half, running back Shane Vereen caught a five-yard touchdown pass because the Broncos had three defenders on Gronkowski.

NFL GameRewind

The Broncos tried covering Gronkowski with nearly every defender in their back seven. There is no doubt he is a matchup nightmare, but Del Rio didn’t seem to have a good plan to slow him down. As a result of changing up the responsibilities, the Broncos made a lot of mistakes.

The offense and special teams didn’t help a defense that is used to playing with a lead, but Del Rio didn’t do his defense any favors with his game plan. It’s safe to say that Brady and offensive coordinator Josh McDaniels have Del Rio’s number in New England.