Du Plessis' comments came after Sri Lanka thrashed South Africa 2-0 in the recently-concluded two-match series, where the fast bowler could only manage to add two wickets in his tally.
"It was frustrating for Dale because he gives everything. You saw when he was running in, there was nothing happening for him, there was no reverse swing and no pace on the wicket. He kept trying," Sports24 quoted du Plessis, as saying.
"I think the next time he has the red ball in hand there will be a little more assistance when we play against Pakistan. I know he is motivated and I expect him to come back and put in the good performances," he added.
The right-handed batsman, however, defended Steyn's performance against Sri Lanka by insisting that it is really difficult to get something out of dusty tracks and that it was unfair to judge the bowler on the same.
"I think it will be unfair to judge our seam bowlers on these conditions, it was really tough for them, they tried hard but it was really tough to get something from the wicket," he said.
"The wicket was quite dusty... our pace factor that we had as our threat was not a weapon in these conditions," he added.
It should be noted that Dale Steyn is just one wicket away from surpassing Shaun Pollock's record of 421 wickets to become the leading Test wicket-taker for South Africa.
South Africa are slated to play three-match Test series against Pakistan, beginning December 26 at the SuperSport Park in Centurion.
(With ANI Inputs)