PITTSBURGH -- Pittsburgh Steelers offensive coordinator Randy Fichtner doesn’t have an official No. 2 wide receiver.

He doesn’t believe in numerically labeling his receivers.

He does, though, believe in having superheroes.

“You look across the league, and everyone has to have at least one Superman and one Batman,” Fichtner said. “It’d be nice to have two Supermen.”

With the departure of Antonio Brown, JuJu Smith-Schuster is one Superman heir apparent, but the other is still writing his origin story.

Halfway through his rookie season, Diontae Johnson is emerging as the other half of the Steelers' next dominant wide receiver duo.

“He’s made his opportunities,” Fichtner said. “I don’t really put a number on him. ... I know there’s going to be games that present opportunities and you need to make your plays. If you do, we’re all going to be talking about you that week. If you put the ball in the end zone, usually people are talking about you that week.”

And after a five-catch, 84-yard performance with a touchdown against Miami, people are certainly talking about Johnson this week.

Smith-Schuster had pretty high praise for the rookie receiver a couple of weeks ago.

“He’s a young JuJu,” said Smith-Schuster, a 2017 Pro Bowl player, in his third year with the Steelers.

To most, it’d be a pretty good compliment, but Johnson just rolled his eyes and grinned when he heard about Smith-Schuster’s assessment.

Johnson’s eye rolls are warranted. He’s 140 days older than Smith-Schuster.

In NFL years, though, he’s two years Smith-Schuster’s junior.

“JuJu, he’s just gonna be JuJu,” said Johnson, a third-round pick who had 24 career touchdowns in 38 games at Toledo. “I look up to JuJu, even though I’m older. He’s had a great success in the league so far. I’m learning from him each day. That’s with plays, film, routes and what not. He’s just giving me pieces of information that I can add to my game.”

Smith-Schuster’s mentorship isn’t just helpful for the rookie -- it also stands to benefit Smith-Schuster.

When Brown left in free agency to join the Raiders, Smith-Schuster moved into the No. 1 receiver spot and the Steelers spent the offseason taking applications for a new No. 2.

The Steelers signed free agent Donte Moncrief, but he had four drops in the season-opener and has not lived up to the task. Second-year receiver James Washington, quarterback Mason Rudolph's favorite college target at Oklahoma State, could also be a candidate for that job, but Johnson seems to have the hotter hand right now.

After Week 2, the Steelers saw enough promise in Johnson’s four catches for 42 yards -- including one 17-yard reception against the Seattle Seahawks -- to elevate him to a starting job. In Johnson’s early development, Fichtner sees a path similar to that of Brown’s.

“I can think back to Antonio,” Fichtner said. “He didn’t play early. He did some special teams things and helped our team. And then kept growing. Diontae, maybe by circumstance, has been put in a role a little quicker, but he’s done a nice job.”

Since being named a starter, Johnson has had multiple catches in every game, including a six-catch, 77-yard performance against the Cincinnati Bengals.

“It’s helped me a lot, having another guy on the other side making the plays, doing their job,” Smith-Schuster said. “Creates more opportunities for me.”

While Johnson has been steadily improving throughout the season, Smith-Schuster has had an up-and-down year while the offense focused on the run and short passing game to navigate quarterback changes. Before his 103-yard game against the Miami Dolphins, his season high was 84 yards against Seattle in Week 2. Two weeks after that, he had 15 yards against Cincinnati. And after a 75-yard game against the Baltimore Ravens in which he fumbled in overtime, he had one catch for 7 yards against the Los Angeles Chargers.

“For a lot of guys in the league, being the No. 1 guy and not getting the ball, you just got to stay the course,” Smith-Schuster said Monday. “I’ll say for myself, yeah, as a No. 1 guy, you think you expect more balls. But at the end of the day, if we’re winning games and my team is happy and we’re getting Ws. That’s a game changer.”

Johnson has 25 catches for 296 yards, and Smith-Schuster 30 receptions for 448 yards this season.

“JuJu’s an established player in this league. Diontae’s learning the game," Fichtner said. "Every week, he’s getting better. You see him make some plays. About every week, he’s in a position to make plays.

“I don’t know at what time it’s a breakout and when it happens, but when it does, no one will be surprised.”

The Steelers have had success with wide receiver duos. Before Smith-Schuster and Brown both topped 1,000 receiving yards last season, Brown did the same with Mike Wallace in 2011. Before that, there was Santonio Holmes and Hines Ward, and John Stallworth and Lynn Swann.

Monday’s win against Miami was the closest the Steelers have come this season to having two superhero wide receivers. Smith-Schuster went over 100 yards for the first time this season -- including a 26-yard touchdown -- and Johnson was close behind with five catches for 84 yards and a touchdown.

After weeks of a middling passing offense, partially hampered by the instability at quarterback, the Steelers got back on track with 236 passing yards against Miami. Smith-Schuster and Johnson accounted for nearly 80 percent of those yards.

Further complementing the pass game was a strong run game anchored by James Conner’s 145 yards and score. It was the first time this season that the offense looked whole. There are still plenty of things to tweak and refine, but if anything, Smith-Schuster and Johnson have shown they can be the receiving duo of the future -- even if Fichtner isn’t ready to bestow the official No. 2 wide receiver tag on Johnson just yet.

“I would never put that 1, 2, 3 on any of the guys,” Fichtner said. “I just know that hopefully this week we’ll have one guy playing like Superman [and] we’ll have one guy playing like Batman. And they’re pretty good superheroes in my book.”