PITTSBURGH — The Jets had more than just their “best practice” of the season on Wednesday. They had a “championship week,” according to Brandon Marshall.

The star receiver remains optimistic about his team’s chance to upset the Steelers (3-1) on Sunday afternoon at Heinz Field.

“We had our best practice that we’ve had since I’ve been here in two years . . . ,” Marshall said Friday night at a Project 375 fundraiser in Manhattan.

His foundation helps to promote education and support for mental health issues and advocacy.

“But we truly had the best week since I’ve been here,” added Marshall, who was traded from Chicago to the Jets in March 2015. “I mean, an awesome week. We had a championship week. And usually, when you approach practice that way, it happens for you on Sunday.”

However, the Jets (1-3) will have to face a perennial playoff team without several key players. Receiver Eric Decker (torn rotator cuff) and starting right guard Brian Winters (concussion) have been ruled out. Cornerback Darrelle Revis is doubtful because of a hamstring injury and receiver Quincy Enunwa (knee) is questionable.

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But Marshall insisted the Jets will “be fine.”

“One of the great things about this team is our depth at every position,” he said. “So we’re confident that we can still get it done. No excuses.”

Their quarterback certainly has no excuses.

Ryan Fitzpatrick has an NFL-leading 10 interceptions, nine of which came in the past two games. His erratic performances have caused some to question whether the Jets would be better served by starting former starter-turned-backup Geno Smith.

Marshall maintained that he hasn’t heard any of that chatter and stressed that that type of talk usually exists in locker rooms that are “broken” and don’t have “any leaders.” The Jets, in comparison, have a “strong locker room,” he said, and everyone is focused on getting back to work.

Marshall acknowledged “we’re all to blame” for the Jets’ poor start. Then he asked: “We should all be benched, right?

Marshall also said he understands the fan base’s frustration all too well.

“They should be [down],” he said. “They should be. We should be. But the guys who go to the next level, the teams who are battle-tested are the teams that have these rough patches and they’re able to break through mentally. It’s not a physical thing with us.

“ . . . We just have to continue to have practices and weeks like this. And the special thing about this team is, most teams will fold it up. They’ll fold the tent and call it the season. But it’s the good teams and the good players that have that perseverance and that strength to continue to move forward. We did that. And it was a great week.”