King, originally signed by the club as an undrafted free agent in 2012, spent his first six years with the Raiders. He played 80 games, punting 426 times for 19,941 yards (46.8 average). He pinned 156 punts inside the 20 with 33 touchbacks.
He finished first in Pro Bowl fan voting last year, though he has never made an all-star game.
The Raiders signed King to a five-year, $16.5 million contract extension a year ago. His release saves the Raiders $2.9 million against their cap.
Walford, originally drafted by the Raiders in the third round of the 2015 NFL Draft, played 44 games with 10 starts. He made 70 catches for 768 yards and six touchdowns in his career in Oakland.