fill someone’s shoes
US /fɪl ˈsʌm.wʌnz ʃuːz/
UK /fɪl ˈsʌm.wʌnz ʃuːz/

1.
後任を務める, 代わりを務める
to take someone's place and do their job or duties as well as they did, especially when that person was very good at their job
:
•
It will be hard to fill his shoes after he retires; he was an exceptional leader.
彼が引退した後、彼の後任を務めるのは難しいだろう。彼は並外れたリーダーだった。
•
No one can truly fill her shoes as the head of the department.
誰も彼女の後任を完全に務めることはできないだろう、部門長として。