Topher has been a part of the San Antonio Memorial Hospital crew since its premiere, and – spoiler alert – the Season 3 saw the surgeon getting fired after Paul’s father bought the E.R. from the insurance company, which then led to others resigning in protest.
It’s arguably a strange time for Ken Leung to take his medical leave, as it were, although it also makes some sense.
This saves the writers from having to write him back onto the main staff, and they can give Topher whatever kind of goodbye story they see fit.