Walker filed at $2.6 million.
Walker was 8-11 with a 4.22 ERA in 25 starts in 2016 for the Mariners. He was acquired by Arizona in November with Ketel Marte for Jean Segura, Mitch Haniger and Zac Curtis.
Walker, 24, is 22-22 with a 4.18 ERA in 65 games (62 starts) in parts of four seasons with the Mariners.
Cash Kruth is a reporter for MLB.com. Follow him on Twitter at @cashkruth. This story was not subject to the approval of Major League Baseball or its clubs.