Walker worked quickly and efficiently. He threw 109 pitches and the game took just two hours to play.
With the shutout, Walker bounced back strong after a shaky start last Thursday that saw him give up seven runs (six earned) in five innings against Colorado Springs.
Walker made his Major League debut last year and might have returned to Seattle already this season had he not suffered an impingement in his right shoulder during Spring Training. The injury kept him sidelined much of the first two months of the season.
Walker came off the disabled list in May and has made six starts for Tacoma. With the Rainers, he is 2-1 with a 4.18 ERA. He has struck out 29 batters and walked 10 in 30 2/3 innings.
Teddy Cahill is a reporter for MLB.com. Follow him on Twitter at @tedcahill. This story was not subject to the approval of Major League Baseball or its clubs.