But he has told the big Serb that hard work and concentration will soon see him back on target.
Parker, whose side take on Slaven Bilic's West Brom in crunch battle at the foot of the table tomorrow, said: “We keep his confidence up by constant messages of hard work, knowing where we are this year and understanding the dynamics of this division.
“It's certainly going to be a real test of one's mental state, really, especially as a forward who is used to scoring goals.
“While he has all the capabilities of scoring goals here, at the same time, things can dent that.
“He needs to have some clear non-negotiables in his game and a clear identity in terms of what he brings to a football match every single week.
“Expectation on him and on what he puts on himself can't be just goals.
“He needs to bring a work ethic every day in training, he needs to bring a work ethic on the pitch ever single day.
“People say you earn your luck and that's exactly what happens.
“Of course, he is at this moment had a couple of quieter games.
“But there will be a lot more times this season where he'll have two or three quiet games.
“You need to keep sticking to what gets you out of these moments and what gets you out of them is hard work.
“That's exactly what he'll do."
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