"I've had to get a lot faster real fast," Garoppolo said with a smile.
Drafted in the second round out of Eastern Illinois, he threw just 27 passes as Tom Brady's backup. His behind-the-scenes role has been much more valuable to the team preparing to face the defending champion Seahawks.
"When we play quarterbacks like we're going to see this weekend, that's a huge role for us," defensive coordinator Matt Patricia said. "This is definitely a kind of unsung hero job."
It also was a new one for Garoppolo.
As a college star, he didn't play on the scout team. So when he joined the Patriots he had to start from the beginning. As the season progressed, so did he.
He met on Tuesdays with defensive coaches. He imitated the skills and quirks of quarterbacks as diverse as pocket passers Peyton Manning and Kyle Orton and more mobile quarterbacks like Aaron Rodgers and Andrew Luck.
"I've been, what is it, 18 different quarterbacks?" Garoppolo said. "You just try to do the best you can for the defense You're trying to give them a look and, at the same time, perfect your craft."
The more time running plays in practice, even on the scout team, the more experience a player has that should help him when he gets into the game. Even if he never does, it can be rewarding.
Jim Miller didn't play as a backup to Brady during the 2004 season. But he enthusiastically ran the scout team and ended up with a Super Bowl ring.
"He'd get in the huddle every single day and be like, 'all right, guys. You love football. Let's go,'" said Patricia, who ran the scout team at the time. "And it just set the right tone for everybody to go out and practice extremely hard."
Garoppolo may not have much to do on game days, but he's had to learn how to manage his time during the week. He studies opposing quarterbacks in film sessions so he can help the defense and still has to prepare to play if Brady gets hurt or comes out of the game during a blowout.
"He's been practice player of the week for us a number of weeks, probably could've been more, for the look that he gives the defense," coach Bill Belichick said.
From one week to the next, Garoppolo must forget the tendencies of one quarterback and learn those of another.
The next quarterback's cadence, habits at the line of scrimmage and amount of time he tries to throw to his primary receiver before dumping the ball off to another are part of Garoppolo's imitations.
Does the opponent use an up-tempo offense or huddle after most plays?
The better Garoppolo can copy the opposing quarterback, the better chance a defense has to stop him in a game.
"There have definitely been a couple of times when it's like, 'hey, they did the exact same thing to me in practice. It's paying off,'" he said.
Previous quarterbacks who ran the Patriots' scout team were Matt Cassel, Brian Hoyer and Ryan Mallett. All moved on to other teams.
But when the Patriots took Garoppolo so early in the draft, he was seen as a more likely heir apparent to the 37-year-old starter, even though Brady has said he'd like to play into his 40s.
Meanwhile, Garoppolo is doing more for the Patriots' defense than for their offense.
This week, he helped it prepare for Wilson, a dual threat and a Super Bowl champion.
"It takes you a little out of your comfort zone, that's for sure," Garoppolo said, "but I'm an athlete. I'll make do."
His defensive teammates certainly appreciate that.
"He's given us a great look, whether he's dropping back and trying to make a play, whether it's being zone read and running," safety Devin McCourty said. "Obviously, we're not going to get Russell Wilson in practice but we got a good showing of what we could see on Sunday."
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