The department head hinted that he was too modest a person for the position.
Literal
Department-head [topic-は], that position [target-に] suitable is [target-には] reserved person is [quotative-と] hinted.
ほのめかした means 'hinted/implied.' 控え目な means 'modest/reserved.' ~には signals that for the purpose of being suitable, he is too reserved. A subtle workplace observation.