Late in the second round of last year’s draft, with the 62nd overall pick, New England selected Garoppolo, who had grown up in Chicago’s northwestern suburbs not only admiring Brady but emulating him. With Brady aging and Bill Belichick never having taken a quarterback so high while New England’s coach, Garoppolo arrived at Patriot Place out of Eastern Illinois as the team’s most alluring backup since Brady himself. He represented the future in a more urgent way than others — Matt Cassel, Brian Hoyer, Ryan Mallett — ever did.

Garoppolo performed well in his rookie season in limited playing time behind Brady while preparing for a moment that has come far sooner than New England could have expected.

He is poised to start for the Patriots until Brady is reinstated from a four-game suspension. The N.F.L. handed Brady that punishment on Monday for probably knowing, according to a league-commissioned report, that New England staff members had deflated footballs in an effort to gain an advantage against Indianapolis in the A.F.C. title game on Jan. 18.

Garoppolo, 23, has thrown 27 career passes — 12 fewer than Cassel had when he replaced an injured Brady in the 2008 season opener — but has four months to prepare for the Sept. 10 opener, against visiting Pittsburgh. Those who know Garoppolo well say he will be ready for the occasion, just as he was ready to become a quarterback in high school, as he was ready to star at Eastern Illinois, as he was ready to make his debut last year in a Sept. 29 blowout loss at Kansas City, a game in which he completed 6 of 7 passes for 70 yards and a touchdown.

“He’s one of those guys that surprises you,” said Dino Babers, who coached Garoppolo in his final two seasons at Eastern Illinois and is now the coach at Bowling Green. “He just seems to be able to do more than what you think he’s capable of doing. He gets more out of a situation than what people give him credit for.”