Johnson, 28, has caught a league-high 12 touchdown passes this season and has racked up over 1,300 yards, with many NFL pundits labelling him one of the greatest wideouts to have played the game.
However, rookie Elam downplayed the role that 'Megatron' might play against his Ravens side, citing his age even though he has a potential five or six years of playing left in him.
Elam told the Detroit Free Press: "He's big, fast, athletic, unstoppable and a freak. But he's pretty old, so I don't know how physical he'll be.
"He's a big guy, but he's older. I guess when they get older they're not going to be as physical, you know what I'm saying? We're going to have to be physical, make him uncomfortable."
Ravens veteran linebacker Terrell Suggs did not mention Johnson's age as something to cause concern however, admitting that it may take their whole defensive unit to stop their opponent.
Suggs said: "Megatron. Anytime someone has a nickname like that, you know the kid's real. He's probably, arguably the best receiver in the game, and it's going to take all 11 guys to tend to him on Sunday."
Both sides are battling for post-season spots and sit in second place in their respective divisions.