From there, he slipped into a funk that lasted two months, befuddling people in the organization. He kept dropping the ball (a total of four) and fumbling it (twice), a mysterious downturn for a tight end known for his sure hands.
Coaches and teammates talked to him, offering encouragement and trying to get into his head to see if there was an off-the-field distraction. (There wasn't.) His high school coach in Norcross, Georgia, Keith Maloof, called the slump out of character, saying this week, "You could always count on him. Unbelievable hands."
Herndon finally delivered a slump-busting performance last Sunday, making two acrobatic catches -- the latter a 6-yard touchdown reception in a 34-28 road loss to the Los Angeles Chargers. That he made those grabs after an early-game drop showed a lot of mental toughness.
More than 2,500 miles away, in Florida, Steve McLendon saw a highlight of the touchdown and smiled. The former Jets nose tackle, who has remained close with Herndon and other ex-teammates since last month's trade to the Tampa Bay Buccaneers, fired off a congratulatory text.
"I'm proud of him and his continuing work ethic," McLendon told ESPN. "Even through the adversity he was going through, he was still doing the necessary things, like staying after practice every single day to catch balls. He did extra every single day when most people would've given up and got frustrated. He stayed the course."
The Jets (0-10), enduring their worst season ever, haven't had the opportunity to celebrate a victory. So they celebrate the small things, like Herndon, humble and well-liked by teammates, making that leaping, fingertip catch in the back of the end zone. He looked like a shortstop, rising above the dirt infield to snare a high line drive out of the air. His teammates were happy for him, knowing how much he had struggled.
Herndon is only 24, but this is his third year in the league and expectations were high at the outset, especially after a strong training camp. The Jets figured they'd see the player who flashed so much potential at the end of his rookie year, but one drop led to another, which led to fumbles -- a serious case of the yips. He kept quiet, internalizing everything. He has been that way since high school.
"It's been pretty difficult, but if I sit around and pout and complain after every game, it's not going to help anything," he said. "You have to fight that urge to dig yourself in a hole. You have to continuously preach to yourself that you're better and you can do better."
Herndon said he enjoyed his "few sparks of success," but he was hesitant to discuss his breakout game in Los Angeles. He didn't want to put the focus on himself, especially after a loss.
Herndon's NFL career has been filled with adversity. One month after being selected in the fourth round of the 2018 draft, the former University of Miami standout was involved in a two-car accident on a New Jersey highway. He crashed his SUV into another SUV, flipped his vehicle and slid about 700 feet. He pleaded guilty to drunk driving, received a four-game suspension to start the 2019 season and ended up playing only one game because of hamstring and rib injuries.
"He's had hurdles to keep jumping," said Maloof, who now coaches Herndon's younger brother, Xavier. "Hopefully, that makes him a better person, a better man."
Herndon showed so much promise as a rookie (39 catches, 502 yards, four touchdowns) that coach Adam Gase wanted to make him a big part of the offense in 2019, but that never materialized because of the suspension and the injuries. After the season -- Jan. 3, to be exact -- McLendon had a long heart-to-heart with Herndon. It was McLendon's birthday; that's why he remembered the exact date.
"He was hard on himself," McLendon said. "Because he was out last year, he felt like he let me down. He felt like he let the team down. I told him to look at the word 'hard.' The word 'hard' means, 'How adversity remembers discipline.'"
McLendon kept him reminding him of that acronym. He also kept telling Herndon, "You're something special. You've got a gift."
He showed it last Sunday. They hope the hard part is over.