Walker held visiting Cedar Rapids to one hit while matching a career high with 11 strikeouts over six innings as the Class A LumberKings blanked the Kernels, 3-0.
"I was able to get ahead with my fastball and then basically throw the curveball in the dirt," Walker said. "When you're ahead in the count, you can make hitters swing at bad pitches."
The Mariners' first-round pick in 2010 out of Yupaica, Calif., Walker has fanned 83 batters and allowed 45 hits in 62 innings since joining the LumberKings in early May. Midwest League hitters are batting just .205 against him.
Of the 20 Kernels he faced Thursday night -- two over the minimum -- only seven put the ball in play. He fanned three around a one-out walk to Cedar Rapids shortstop Rolando Gomez in the first inning.
In the second, he struck out Justin Bass, walked David Harris and struck out Brandon Decker before Harris was caught stealing.
After whiffing the first two Kernels in the third, Walker gave up the first Cedar Rapids hit -- and ball in play -- to center fielder Chris Giovinazzo, who singled to right field. Walker then set down the final 10 batters he faced in order, striking out the side in the fifth.
"I felt calmer and looser tonight than in the last couple starts," he said. "You can't get too angry about bad things happening. I'm trying to stay positive and have fun."
Walker improved to 3-4 with his first win since May 26. He did not allow a Kernel to reach second base.
Reliever Tyler Blandford fanned two in a hitless seventh before giving way to Jonathan Arias for the final two frames. Arias allowed a pair of singles to Decker and Jean Almanzar in the eighth and a walk to Bass in the ninth, but was otherwise unscathed. Five of his six outs came via the whiff.
The three LumberKings hurlers combined to fan 18 batters. Clinton's pitching staff ranks third in the Midwest League in strikeouts with 701 in 84 games.
The Clinton offense was led by designated hitter Stefen Romero, who went 3-for-4 with an RBI, a run scored and a stolen base. He was the only 'King to collect multiple hits.
Cedar Rapids southpaw Max Russell also matched a season high in strikeouts with nine, but fell to 4-9 after allowing two runs -- one earned -- on five hits and a pair of walks over six frames. The Angels prospect has lost seven of his last eight outings.