Guthrie allowed only three singles in seven innings, and the Kansas City Royals rolled to a 5-0 win over the Athletics on Tuesday night.
Guthrie, who struck out a season-high eight, ran his scoreless streak to 15 innings, the longest streak of his career. He has yielded eight hits and struck out 14 in his past two starts, victories over the A's and the Chicago White Sox.
Guthrie (5-12) is 2/3 in five starts with the Royals, who acquired him in a July 20 trade with Colorado for left-hander Jonathan Sanchez.
In a June 12 start against the A's at Colorado, Guthrie allowed seven runs and eight hits, including three home runs and two walks in five innings.
"When I pitched against them earlier in the year every pitch I threw was the exact wrong pitch at the wrong time," Guthrie said. "So I had a nice blueprint on what not to do. I don't think I threw too many duplicate pitches of what they punished me.
"I gave up an awful lot of hits and an awful lot of long home runs in a short amount of time. They gave me a blueprint on how to do a better job."
A's manager Bob Melvin noticed the change in Guthrie's plan.
"He's a guy we handled pretty well in Colorado." Melvin said. "He's coming off his best game this year, and he might have been riding some confidence from that. But I'd like to think we could get some better at-bats against him. We didn't have a lot of good at-bats tonight.
"He worked ahead and had a good downward plane on his fastball, good movement."
Guthrie, who is eligible for free agency after this season, could be pitching his way into the Royals' plans for next year.
"I just felt along with Dayton (Moore, general manager), three or four starts and that would get him back on track," Royals manager Ned Yost said. "He's definitely on track. It's not really fluky stuff. You can see where this could be extended out start after start. I'm really liking what I'm seeing right now."
Guthrie was 4-11 with a 6.31 ERA as a Rockies starter. He credits Royals pitching coach Dave Eiland for helping him with adjustments.
"Had I not come over here and been able to work with those types of people, I might still be banging my head and still be making the same mistakes." Guthrie said. "It wasn't about getting settled in as much as it was getting better and making some adjustments."
Tim Collins and Greg Holland completed the shutout for Kansas City. Collins struck out all three batters he faced in the eighth inning, boosting his total to 77 -- a Royals' strikeout record for a left-handed reliever.
The A's failed to get a runner past second base and were shut out for a major league-leading 14th time.
A's rookie right-hander Jarrod Parker (7-7) was pulled after 4 2/3 innings. He gave up five runs, five hits and two walks. Parker is 2-4 with a 6.15 ERA, and batters are hitting .309 against him in his past seven starts.
He was 5-3 with a 2.46 ERA and an opponents' batting average of .209 against him in his first 13 starts.
In the third inning, Josh Donaldson and Coco Crisp singled, but Donaldson was put out in a rundown between second and third. Right fielder Jeff Francoeur earned his 13th assist on the play, tying him for the major league lead among outfielders.
The A's placed 3B Brandon Inge on the 15-day disabled list with a sprained right shoulder. Inge joins eight teammates on the DL. The A's have used the DL 19 times this season. ... Oakland recalled INF Josh Donaldson from Triple-A Sacramento, where he was hitting .335 in 51 games. ... The Royals asked for unconditional release waivers on INF Yuniesky Betancourt, who was designated for assignment on Aug. 5 with a .228 batting average. ... Cain became the 13th Royals player to bat eighth. ... A's RHP Brandon McCarthy, Wednesday's pitcher, will make his second start since coming off the disabled list. McCarthy, who was out because of a shoulder strain, is 6-0 with a 2.25 ERA in his past eight starts. Rookie LHP Will Smith will start for the Royals.