YOUNG ARM OR THE VET?

Will it be Ryan Fitzpatrick? Or Bryce Petty? In a few hours, we’ll find out.

Jets coach Todd Bowles said Friday that he won’t make a decision on his starting quarterback for Sunday’s game against the Rams until just before game time.

Fitzpatrick, who sprained his left MCL during last week’s loss to the Dolphins, said earlier in the week that he was “definitely optimistic” about starting. But after three days of being limited in practice — and splitting about half of the reps with Petty — Bowles wasn’t ready to make definitive announcement.

If Fitzpatrick does play, he’ll have to wear a knee brace. “Fitz is Fitz, he’s mentally on top of things and we’ll just see where he is physically,” offensive coordinator Chan Gailey said.

Injured or not, Fitzpatrick can’t play any worse. He leads the NFL with 13 interceptions and has the lowest quarterback rating (67.6) — worse than even Blaine Gabbert. The Jets (3-6) are eager to get back on track against the Rams (3-5). But to do so, they’ll beed a strong effort from their quarterback — whoever he might be.

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Gailey, Fitzpatrick’s former head coach in Buffalo, wasn’t the least bit surprised that the 12-year veteran is determined to play. “I know that’s the way he’s always been his whole life,” he said. “That’s how he’s gotten to where he is.”

ROOKIE MISTAKES

The Jets aren’t giving up on Jalin Marshall.

Despite the rookie’s issues with ball security, the coaching staff remains confident in Marshall. “(It’s) well known in the room that you got to catch it, you got to make good decisions, and if you don’t you’re not going to be out there. But at the end of the day, Jalin’s done a pretty damn nice job,” special teams coordinator Brant Boyer said. “He’s a young player that’s working on it, and he’s going to continue to get better. Nobody is a this finished product . . . He’ll do a better job and I’ll do a better job of coaching.”

Marshall went undrafted out of Ohio State and made the final 53-man roster as the Jets’ punt and kickoff returner. But his erratic play hasn’t gone unnoticed: He had a 65-yard kickoff return in the season opener against the Bengals, but he had back-to-back fumbled kickoff returns that were returned for touchdowns against the Bills and Chiefs. Marshall also suffered a torn labrum in Kansas City that sidelined him for several weeks.

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But last week, he caught his first NFL TD — an 18-yard, fourth-quarter score that put the Jets ahead 23-20 over the Dolphins with six minutes to play — and finished with a career-high 59 receiving yards on three catches.

“I think he’s developed too and we’re gaining more and more confidence in him, so if he can continue to develop, that would help us a lot,” Gailey said. “ . . . You don’t put a guy in the doghouse — there might be a paw in there, but you don’t put a guy totally in the doghouse because of something that happened.”

BIG APPLE-BOUND

For the first time since 1992, the Jets will square off against the “Los Angeles” Rams. The Rams, who played in St. Louis from 1995-2015, hold a 9-4 series advantage. The last time the Jets faced the “Los Angeles” Rams was on the road on Sept. 27, 1992. They lost 18-10.

X-FACTOR

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Ram DT Aaron Donald

How big of a challenge is it to stop Aaron Donald?

“Huge,” said Gailey. “He is one of the best that I’ve seen this year.”

Donald is one of the most skilled players in the NFL and a physical presence who’s nearly impossible to stop. He also has team-high five sacks, which is tied for eighth in the NFL and is second only to Jets’ Leonard Williams (six) among defensive tackles.

“Very quick, very fast, very powerful,” Bowles said of Donald. “Smart player, tough player, knows how to get after it.”

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Added Gailey: “He’s always going forward. There’s no sideways to this guy . . . He has really got a unique twitch about him that allows him to be able to that and rush the passer. He’s special.”

SPEED DEMON

Jets special teams coordinator Brant Boyer has had “a lot of sleepless nights” preparing for Rams receiver/returnman Tavon Austin. “The guy’s a special guy,” Boyer said of Austin. “If he’s not the best punt returner in the league, I think he’s really close. He’s got all of the tools . . . He’s a special athlete that can win in space.”

The could be an issue for the Jets’ special teams coverage, which was poor last week. The biggest breakdown was Antonio Allen’s offside penalty, which led to a re-kick and a 96-yard kickoff return TD by Miami’s Kenyan Drake. “We didn’t get the job done and we let our team down,” Boyer said of the decision to kick the ball at Drake on the second attempt. “That’s on me.”

GOFF GROUNDED

The Jets aren’t the only team keeping their rookie quarterback on the bench. The Rams selected Jared Goff with the No. 1 overall pick in this year’s draft, but NFL.com recently reported that coach Jeff Fisher won’t play the rookie until his team is eliminated from playoff contention. Instead, the Rams are riding the not-so-hot Case Keenum, who has nine touchdowns and 11 picks.

Meanwhile, Jets’ second-round pick Christian Hackenberg has also been riding the bench. The organization essentially wants this to be a redshirt season for the former Penn State signal-caller.

2,445 — Roughly the number of miles the Rams will travel between Los Angeles Memorial Coliseum and MetLife Stadium — the longest distance any opponent has had to travel this season to face the Jets

36 — Negative rushes by the Rams defense (second-most in the NFL)