United Kingdom, March 21 -- Sarah Michelle Gellar has paid tribute to her Buffy the Vampire Slayer co-star Nicholas Brendon, following his sudden death.

The 54-year-old star, who was known for his portrayal of Xander Harris in the supernatural horror TV series, passed away "in his sleep of natural causes" on Friday (20.03.26) and Gellar - who played Buffy Summers - took to Instagram to remember him.

She posted a picture of them together and wrote: "'They'll never know how tough it is to be the one who isn't chosen. To live so near to the spotlight, and never step in it. But I know. I see more than anybody realizes, because nobody's watching me'. I saw you Nicky. I know you are at peace, in that big rocking chair in the sky."

Their co-s...