The Jets’ season could rest on Trevor Siemian’s shoulders.

With Sam Darnold declared out for Monday night’s game against the Browns and likely out multiple weeks with mono, the Jets will rely on their backup quarterback — who hasn’t played in a regular-season game since 2017 — to navigate a daunting early-season schedule. Already 0-1 after a home meltdown against the Bills, the Jets host the talented Browns, before traveling to New England — then a bye week — and Philadelphia.

So, who is it that’s replacing the Jets’ second-year franchise quarterback?

Well, the 27-year-old Siemian was selected in the seventh round (250th overall) out of Northwestern by the Broncos in 2015, and earned a Super Bowl ring as Peyton Manning’s backup. Following Manning’s retirement, Siemian won a quarterback competition with first-round pick Paxton Lynch and ex-Jet Mark Sanchez in 2016 to become Denver’s starter. Over the next two playoff-less years, Siemian made 24 starts, posting a 59.3 completion percentage with 30 touchdowns, 24 interceptions and a 79.9 quarterback rating.

Before last season, Siemian was traded to the Vikings, and spent the season on the bench behind Kirk Cousins. Siemian then signed a one-year, $2 million deal with the Jets this offseason and appeared in all four preseason games, completing 25 of 32 passes for 158 yards with one touchdown and no interceptions.

The Florida native, who considered attending Harvard before becoming Northwestern’s first NFL starting quarterback since 1979, was named an alternate for the 2017 Pro Bowl, but was forced to decline due to a recent shoulder surgery.

The Jets promoted Luke Falk from the practice squad to serve as Siemian’s backup. Falk, a 2018 sixth-round pick, has never played in a regular season game, and has previously been waived by the Titans and Dolphins.