During the Patriots' win over the Broncos last Sunday, there was a play where New England lined up in a three-wide receiver set with one tight end on the line of scrimmage and one tight end in the backfield behind quarterback Tom Brady.
Clear pass formation, right? Three receivers on the field, an explosive pass-catcher in Rob Gronkowski on the line and the tight end in the backfield (Aaron Hernandez) had just eight career carries entering the game.
There's no way the Patriots run the ball there. Except they did.
Hernandez got the handoff, ran off left guard and rumbled down the sideline for a 43-yard gain.
Ravens defenders say a play like that is one of the main reasons why the Patriots' offense is so tough to defend. Not only do they have elite talent, but they can run any play out of any personnel grouping at any time, complicating things for their opponents.
"They are not your typical offense," linebacker Jarret Johnson said. "Personnel groups are a big thing in our league. Identifying who is on the field is huge. Normally, when you get a certain personnel group, you pretty much know where the guys are going to line up. They'll give you a personnel group and line up nowhere close to what you think they are going to do. You just have to roll with it and know what's coming and adapt to it.
"That's why communication in these games is so vital and not going crazy and overthinking things - just getting lined up and playing - because you can get anything. You don't know what you're going to get."
One thing which allows the Patriots to be so versatile in their offensive play calling is that they're probably as athletic as any offense in the league.
New England has a quick, shifty wide receiver in Wes Welker who was second in the league in receiving yards this season. They have a speedy veteran receiver in Deion Branch, who can stretch the field and has come up with a number of big plays over the years. They have Gronkowski, who is built like a defensive end at 6-foot-6, 265 pounds but has the hands and agility of a wideout, and Hernandez, who is probably the more explosive of the two tight ends in terms of his ability to get up the seam.
They also have three capable running backs who can all catch the ball, as well. Add it all up, and there are weapons all over the place for Brady to look for in the passing game.
"They're very multiple in what they do," head coach John Harbaugh said. "And, they are a very (good) self-scout team. They understand their tendencies, they build them, and then they rank them. It's a very clever offense. It's well put together."
Gronkowski and Hernandez have been especially crucial for the Pats this season. Between the two of them, they combined for over 2,200 and 24 touchdowns, and they allowed New England to turn what were once obvious running formations into passing ones.
"If you watch SportsCenter, you've seen their offense," Ravens linebacker Jarret Johnson said. "They can hurt you in 100 different ways. They use their personnel groups really well, whereas most teams, when they go two tight ends, it's usually a somewhat running formation or at least a balanced formation. They can do anything.
"It's a big predicament for us. It's a challenge, but it's what you like, because we can be a challenge, too."