Diontae Johnson only played in 50 snaps during the first two games of his rookie season in 2019, making four total catches, one of which—his longest—came from Mason Rudolph. He caught three of five targets from Ben Roethlisberger during that time. All three came on third down and all three failed to convert.
Needless to say, these two weapons of the Pittsburgh Steelers offense still need time to work together, though through two games so far this year he has caught 14 passes on 23 targets for 149 yards and a touchdown. The catch percentage needs to tick up, but it will take both to work on the connection and make it the best it can possibly be.