Tony Pulis has said that Saido Berahino has been unable to find his form after missing out on a move away from West Bromwich Albion in the summer.
The 22-year-old threatened to go on strike after a proposed transfer to Tottenham Hotspur fell through on deadline day.
"He's still not near what he was at the back end of last season," Pulis told reporters.
"His form has dropped and dipped but the penny's dropped and he has to be switched on.
"The opportunity of going to a top-four or five club, and not getting a move that he thought was going to just happen, really shook him."
The England Under-21 international has scored just three times so far this season.