The constant, as it has been in the Patriots-Jets rivalry for almost two decades, is 41-year-old quarterback Tom Brady.
Consider this contrast:
If Brady faces Darnold, it will mark the largest age gap (19 years, 306 days) between two starting quarterbacks facing one another since the 1970 merger, according to the Elias Sports Bureau.
If Brady faces McCown, it would mark the second-largest combined age (80 years, 258 days) of two starting QBs since the 1970 merger, per Elias. The only quarterback matchup with a larger combined age was Vinny Testaverde (44) vs. Brett Favre (38) in 2007 (82 years, 44 days).
Naturally, Patriots coach Bill Belichick is preparing his team for both options.
"Every week, we’re one play away from playing the other quarterback, whoever the starter is," he said. "So we have to be ready for both guys. That’s the way it is every week."
Belichick's impressions of Darnold?
"A big, strong guy, he’s got a good arm, [can] make all the throws. A lot of talent," he said.
"Smart, really handles himself well," Belichick said. "He’s always had a lot of responsibility at the line of scrimmage to audible plays, change protections, things like that. I think he sees the defense well, certainly knows what they’re doing. He’s got a good arm, he’s got good size, athletic, can avoid the rush, make plays out of the pocket ... Everybody that’s been with him seems to have a lot of respect for the way he carries himself and the way he prepares and all that."
With some teams, the differences in style of play between starting and backup quarterbacks is extreme, such as the Baltimore Ravens this year (traditional pocket-passer Joe Flacco vs. Lamar Jackson, who is more of a runner).
As for what Belichick sees in the differences between Darnold and McCown, he said, "They’re both good. I mean, we played against McCown last year, and he did a really good job against us down there. Obviously, Darnold -- I mean, this is an explosive team. They’ve had four or three games where they’ve hung up a lot of points -- 30s, 40s -- so they can move the ball, they can score points."