The £98m signing has hit a slight plateau in recent weeks with no goals in six Premier League games for the Blues.
"We are in the process of adapting to each other. In this moment I feel like Romelu has been overplayed, I think he played too many competitions over the summer, too many competitions with the national team and now the Nations League," he said ahead of their Champions League tie with Malmo.
"He is a fantastic athlete and such a competitive guy, he digs in deep, he wants to win these things, he wants to be out there and win.
"He wanted a good outcome with Belgium, this was a huge match for him personally, it means a lot for him to play for his country.
"He always put it on his shoulders but I feel he is a bit tired mentally, he does not fully enjoy without having second thoughts.
"For me he has been overplayed but once he finds his rhythm and once he finds things a bit easier... but it is difficult to judge if he really needs a break or if we need to keep him on the pitch."
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