During a stop by "The Graham Norton Show," Smith addressed speculation he might be leaving the iconic BBC science-fiction series "Doctor Who," TVGuide.com reported.
"No, I am very happy to stay. I love it and love making the show," Smith said, emphasizing he will be sorry to see Gillan go.
"I'll miss Karen because she's my best mate," he said. "She's mad as a box of cats, but she's a firecracker!"
"I've known for a while," he said of her departure. "There comes a time when a story reaches its conclusion, and the essence of the show is that it constantly reinvents itself."
Smith's current contract insures he will appear in at least 14 more episodes to run in 2012 and 2013.
Gillan and Darvill have played couple Amy Pond and Rory Williams since Smith took over the role of the time-traveling Doctor early last year.