Johnson says Salah made the wrong choice too often against Burnley at Anfield as the Reds dropped their first points in the league at home all season.
"I think he was [trying too hard in the quest for the Golden Boot], literally that," Johnson told Sky Sports.
"He was trying to guide the ball in as supposed to just getting through it sometimes.
"And we know that he is on track to fight for this Golden Boot. So, I think he got into a couple of opportunities where, months ago, he would have scored without even thinking about it.
"But today, he did look like he was trying to guide it in and sort of take the easy option rather than sometimes put his foot through it."