With the D-backs having provided Webster with a three-run lead before he even took the ball, Harkey wanted him to throw the ball down the middle and let the natural sinking movement on his pitches carry it to the corners.
Webster took the advice to heart and retired the next 14 hitters he faced as the D-backs beat the Giants for the second straight day.
"Just told him to use his sinker more in the middle of the plate, because starting it on the black, it's never a strike, so hitters won't swing at it," Harkey said. "You won't get many swings that way. He made a good adjustment."
Webster was recalled from Triple-A Reno to take Josh Collmenter's spot in the rotation. Acquired from the Red Sox in December as part of the deal that sent Wade Miley to Boston, Webster had a rough spring for the D-backs.
There were struggles on the mound and off it as he suffered through a couple of bouts of illness. After being assigned to Reno, he made two starts before being placed on the disabled list with shoulder fatigue.
"I've definitely had a rocky road so far," Webster said. "So I'm happy to show them this and hopefully we can feed off this and do it again."
Webster (1-0) had a no-hitter through 5 1/3 innings, but following a one-out walk to Nori Aoki in the sixth, Joe Panik doubled down the right-field line for the Giants' first hit.
Webster would not get out of the inning as the Giants managed to score two runs to pull to within two.
D-backs manager Chip Hale started Jarrod Saltalamacchia behind the plate in an effort to provide Webster with some comfort. Saltalamacchia had worked with Webster earlier this year in Reno.
The move definitely helped Webster after the shaky first inning as Saltalamacchia talked to him in the dugout during the top of the second.
"I was still trying to feel it out and I'm not going to lie, I definitely had the jitters," Webster said. "When I came back in the dugout, Salty was able to settle me down and we got out there and got in a good rhythm together and we just rolled with it."
When they acquired him, the D-backs had high hopes for Webster, and despite his poor spring and 9.00 ERA with Reno, the team still believed in his potential.
"I don't really think he came out of Spring Training healthy," Harkey said. "So we really didn't get to see the Webster that everybody had talked about. He's always been a guy who's been on the verge of having command, not having command and hopefully with a little more success, he can build on it."