Walsh explained that she left Greys Anatomy in order to lead its spin-off series, Private Practice.

She would continue playing the character of Dr Montgomery after she left Seattle Grace to set up in Oceanside Wellness Centre, California.

Upon hearing the news of a spin-off, Walsh said: I was shocked and excited and mostly just totally blown away.

Then I was nervous, like, Wait, really? Why me? But mostly I was just thrilled because it totally felt like the right thing.

I was so flattered and honoured that they would think of my character to take off for greener pastures.

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Grey's Anatomy: Why did Kate Walsh really leave Grey's Anatomy? - Express