The Steelers were one of the league's most explosive offenses a season ago. The unit ranked sixth in the league in efficiency, according to Football Outsiders' metrics, and Ben Roethlisberger was a top-five quarterback in part because he was throwing passes to Antonio Brown.

It was a similar story in 2017; the offense ranked No. 3 overall because of familiar faces: Roethlisberger, Brown and running back Le'Veon Bell, who was fifth in total value as a runner and nearly as valuable as a receiver.

But Brown, who was unhappy in Pittsburgh and didn't hide that fact, has since been traded to Oakland. Also gone: Bell, who sat out the entire 2018 season because of a contract dispute and signed with the Jets this spring. And just like that, two of the most dynamic playmakers in the NFL were off the Steelers' roster. 

Pittsburgh unofficially moved on from Bell when he no-showed last season; his replacement, James Conner is now the unquestioned top dog in the Steelers backfield. He showed that in 2018 and when it was over, Conner rushed for 973 yards, had another 497 receiving yards and scored 13 total touchdowns. Conner made $578,000 in 2018. Bell, who made $12.1 million in 2017 on the franchise tag and would have made more than $14 million last season, put up 1,291 rushing yards, 655 receiving yards and 11 touchdowns in his last year in Pittsburgh. Put another way: Conner, who is four years younger than Bell, isn't a bad consolation prize.

That said, the loss of Brown has something to do with the current Super Bowl odds -- the Steelers are at 20-to-1, which is behind the Browns (!) at 16-to-1. And that brings us to one of the biggest questions facing Pittsburgh ahead of the 2019 NFL season: How can they replace Brown, who has been one of the NFL's most productive players over the last eight seasons?

It starts with Ben Roethlisberger, who enters his 16th NFL season. And even though he's 37, he's still one of the NFL's best passers. A season ago, he threw for a career-best in yards (5,129) and touchdowns (34) and ranked fifth in total value among all quarterbacks, behind only Patrick Mahomes, Drew Brees, Philip Rivers and Matt Ryan. But the veteran quarterback also knows that his current cast is more than capable of putting up similar numbers. And that conversation starts with JuJu Smith-Schuster.

JuJu Smith-Schuster

Fun fact: In his second NFL season Smith-Schuster led the Steelers in targets (168), receptions (111), yards (1,426) and was No. 2 in total scrimmage yards behind only James Conner. On 10 occasions he had double-digit targets in a game and in the Steelers' final seven regular-season games he had at least 100 receiving yards four times (including 189 yards against the Broncos in Week 11). The biggest issue facing Smith-Schuster ahead of 2019 is whether he can be this productive without Antonio Brown, who regularly required double teams, also on the field. If the rest of the offense steps up there's no reason this group can't be just as explosive.

And while Smith-Schuster is the unquestioned No. 1, who will step into his previous role as the Steelers' No. 2 target? 

James Washington

Washington had a forgettable rookie season -- he had 16 receptions, 217 yards, a touchdown, and his quarterback call him out after a huge drop -- but according to his teammates the former second-round pick looks like a completely different player ahead of the '19 campaign.

"But you talk about a young dude who's up and coming, it's going to be James Washington," Smith-Schuster told ESPN recently. "A guy from Oklahoma State, came to the Steelers his rookie year, started off slow but figured it out and got the ropes down. This past summer workouts that we had, he's been doing amazing, a great job. I'm super excited to see how he does this year. He's our guy that's going to sneak up on everybody." 

At the combine, Steelers general manager Kevin Colbert spoke about Washington's rocky rookie campaign as well as the organization's faith in his abilities.

"James had a rough start," Colbert said in February. "I mean, it was disappointing because he was dropping balls that he didn't drop in college. James had I believe 35 touchdowns at Oklahoma State when he played with Mason Rudolph and was a very productive player, but he also went through an adjustment and learning of the NFL game and he fought through it week after week. He had the big drop at Denver, where he probably should have just run through the ball. He probably would have scored. But his confidence after that game grew to where he was a contributor down the stretch. So, not uncommon for rookie players to go through that, but we had no question about James Washington's ability to catch the football and now he's starting to show that."

If Washington looks anything like the deep threat he was in college he'll open things up for the rest of the passing game. If the adjustment from college to the NFL lingers into Year 2, the Steelers have an insurance policy in Donte Moncrief.

Donte Moncrief

Moncrief's career can kindly be described as replacement-level; a burner coming out of Ole Miss, he has yet to live up to expectations during his five years in the league. His best season came in 2015, with Andrew Luck, when he had 64 receptions for 733 yards and six touchdowns. In 2018 with Blake Bortles and Cody Kessler throwing him passes, Moncrief had 48 catches for 668 yards and three scores. Now in Pittsburgh, and on the receiving end of passes from Ben Roethlisberger, the sense is that Moncrief's best football could still be ahead of him.

"For a guy that hadn't been in the system, he's really done some things that are innate," Steelers receivers coach Daryl Drake said recently, via the Pittsburgh Tribune-Review. "He does some things that come natural. Picking up the system, there are times when you get a guy, you bring him in and he's been in two or three different systems and those systems start running together. But he's been able to distinguish the differences and go out there and do things that make my job a lot easier because he has a feel for the position. One thing he's doing is playing with a lot of confidence, and Ben has confidence in him. He's just got to continue to grow."

Diontae Johnson

The Steelers have had some success drafting receivers out of the MAC (see Brown, Antonio) and Johnson, their 2019 third-round pick out of Toledo, could be the next find.

"The one thing I noticed was he caught every ball I threw to him, I even threw him some bad balls on purpose, throw some high, behind him, just to see if he would catch them," Roethlisberger said during minicamp, via the Pittsburgh Post-Gazette. "And he caught every one. It was impressive."

Veteran cornerback Joe Haden added: "For me, (Johnson) runs some really, really crisp routes. He is natural. He is fast. He comes out of his breaks really well. He has been impressive. I watch receivers. I watch tape on them. He is a good one."

Ryan Switzer

Switzer, who was traded from Oakland to Pittsburgh before the '18 campaign, was ready to retire before he became an integral part of the offense. He had 36 receptions for 253 yards and a touchdown in his first year with the Steelers and now he's vying for more playing time and would embrace a chance to be the Steelers' No. 2 option.

"It takes a different kind of guy to work the middle of the field, be able to be on the same page as the quarterback," Switzer, who also returns kicks, said this month, via Triblive.com's Jonathan Bombulie. "There's a lot of different reads and a lot of different adjustments you've got to make in the middle of the field. I'm getting the hang of it. I'm, obviously, not there yet, but I'm working on it. ...

"The more reps that you get, the more game experience you get, the better the feel and the better you get," he continued. "It helps when you've got a quarterback who's done it for a long time and has a lot of experience in that area. He's kind of molded me as the year went on. I'm learning from those experiences. Hopefully, we'll put them to the test this year."