I don't think there will be a major slump.
He didn't have a high percentage on base guy in 2017 like DJ in front of him, and he didn't have Stanton in 2017 hitting behind him either.
Point being, opposing pitchers could pitch around him in 2017, or make him chase.
If DJ gets on, and he does with regularity, pitchers have no choice but to come into Judge, unlike 2017.
You pitch around Judge with DJ on base, pitchers are looking at a potential five run first inning with that lineup.
You go down 5-0 in the first, forget about it, game over.