Trailing 23-17 after a Dilfer interception was returned for a touchdown by Perry Phenix, the Ravens had the ball on their own 30 with 2:18 on the clock.
"I told the defense: 'When I come back, I'm coming back with seven points,' " he said later. "A situation like that, they don't believe you.
"But I've been in situations like this so many times with John."
Nine plays later, Johnson made amends for dropping an almost-certain long touchdown pass by catching a game-winning 2-yard throw from Dilfer with 25 seconds left.
It was left for kicker Matt Stover to add the biggest extra point of his season - after Tennessee's Al Del Greco missed his and a subsequent 43-yard field-goal try at the gun. The Ravens' drive may prove to be the biggest of the season, for what it accomplished and what it meant.
"Shannon was so calm in the huddle," said Johnson, the Ravens' third-year wide receiver. "It was amazing to see how calm he was. Trent was poised and calm. They really led us down the field."
The victory boosted the Ravens to 7-4 and within 1 1/2 games of the first-place Titans (8-2) in the AFC Central. It was Tennessee's first-ever loss at Adelphia after 12 straight wins. But more importantly, it stamped Baltimore as a viable playoff team in the AFC.
The Ravens will play four of their last five games at PSINet Stadium, a reward for their arduous early-season road schedule.
At the least, the Ravens are armed with newfound confidence for the stretch run.
"This is a tad bigger than September's comeback victory over Jacksonville just because of the situation we're in," said defensive end Michael McCrary. "This is no longer the old Ravens, where we'd lose a game like that at the end. For our offense to be able to keep its poise and patience twice this year is absolutely amazing."
Dilfer was a big part of the poise equation. The seven-year veteran hit 23 of 36 passes for 281 yards, including a perfectly timed, 46-yard touchdown strike to Qadry Ismail in the first quarter.
"Poise has a lot of different faces," Dilfer said. "For some, it's that bland stare and undying confidence. For others, it's an absolute will.
"For me, poise is just trusting the people around me. I've lacked poise in my career because I didn't trust what's going on around me. I told these guys I've worked my whole career to play with a bunch of guys like this."
Dilfer had a sense of deja vu, too. With the score tied at 17 in the fourth quarter, linebacker Peter Boulware had stripped Titans quarterback Steve McNair of the ball. Defensive end Rob Burnett recovered at the Tennessee 22.
But on third down from the 19, with the Ravens positioning for a Stover field goal, Dilfer threw an interception that was returned 87 yards by Perry Phenix for a go-ahead touchdown. The intended receiver was Johnson.