Doug Flutie has shared office space with both Tom Brady and Matt Cassel, when the three quarterbacks worked together during the 2005 NFL season. So for those curious as to how the Patriots' offense will look with Cassel taking the reins, Flutie offers a worthy perspective.
Will they morph from a spread-the-field passing attack to a grind-it-out, run-based approach? Will they still feature a lethal no-huddle offense? Might there be more trickery?
To answer those questions, Flutie starts on Page 1 of the team's playbook.
Echoing the words of offensive coordinator Josh McDaniels, he makes the point that the Patriots are a game-plan offense, meaning they tailor their approach specifically toward the weaknesses of that week's opponent. That runs in contrast to other teams that have less variety but are particularly difficult to stop in one area because they do it so well.
So when it comes to the Patriots, it's a chameleon-like style. It is particularly ambitious, but having a player of Brady's caliber made it possible to execute.
Can they do the same with Cassel?
Flutie believes the answer is yes, although it likely will come with some modifications.
"I think the world of Matt and I think he can handle it," said Flutie. "He knows that system and he can make all the throws. So I don't think you change anything, but you may limit it somewhat because he hasn't run all the stuff that Tom has before."
Longtime NFL coach Dan Reeves, who served as a radio analyst for Sunday's Patriots-Chiefs game, said he didn't notice any major schematic changes when Cassel replaced Brady. If anything, Reeves felt the Patriots were a bit more committed to the run with Cassel, and statistics reinforce that point: With Brady at quarterback, 11 passes and four runs were called, and with Cassel, it was 18 passes and 22 runs.
While the play-calling might have been a bit different with Cassel - more conservative - the formations and personnel groupings were indeed the norm.
Of the team's 58 offensive snaps, 44 came with three or four receivers spreading the field. The Patriots were in three- or four-receiver packages 68 percent of the time last season, so they eclipsed that pace against the Chiefs.
It wasn't as if the Patriots decided to protect Cassel by loading up at the line of scrimmage with extra tight ends.
Reeves himself twice had situations in which his starting quarterback was injured and the backup had to emerge - with the Broncos' John Elway in 1992 and the Falcons' Michael Vick in 2003. In Denver, then-rookie Tommy Maddox stepped into the primary role for four games, and Reeves recalled that coaches simplified the team's attack.
Reeves, like Flutie, projects that the Patriots will scale back some of their plans with Cassel, but he's not sure how much.
"With Tom Brady, they change week by week what they do because he can handle so much," said Reeves. "Matt has been in the system now for four years and maybe he can, too. It will be interesting to see."
One area the Patriots might limit is the no-huddle offense, which is a Brady specialty and has been a major part of the team's arsenal because it sets the tempo and doesn't allow the defense to substitute. Brady is like a conductor of an orchestra in that setting, combining a unique mix of calmness and urgency while ensuring that all 11 players on offense are working in unison.
Part of the reason the Patriots are so comfortable going no-huddle is one of the less talked-about but most impressive parts of Brady's game: His ability to read a defense and get the team into the right pass protection and play.
"That is a huge part of their offense, a huge part of football today, and Tom always amazed me with that - making the calls to pick up blitzes," Flutie said. "The speed in which you recognize and change protections and get the offense into the right play is very important.
"Matt gets all that, he understands how to do it, but the thing is [getting the repetitions], and being in that position when that play clock is ticking down. The more you do it, the more comfortable you get. That was frustrating for me when I came to the Patriots. I remember staying late, especially during training camp, to walk through mentally on my own."
Naturally, because Cassel doesn't have that game experience, there could be some growing pains in that area. The Patriots likely will be judicious in how much they put Cassel into those situations, which could lead them more into a manage-the-game type of approach in which they take fewer chances on offense and lean more heavily on their defense and special teams.
"I think Matt will improve week by week in terms of his comfort zone," Flutie said. "I don't think he's intimidated by any situation. I really think he's very cool-headed, very confident.
"That being said, the biggest difference is that Tom could fall back on past experiences and even get you into a play occasionally on his own. Or he could walk over to the sideline to Josh and say, 'Remember we ran this against Pittsburgh last year? We should try to do this.'
"So the game-adjustment type of thing will be an area that will be different, but only because Matt hasn't had that experience. They shift game plans week to week but there is always an occasion when things come up and they could throw new stuff at Tom on the fly, where maybe you can't do that with Matt."