Guthrie, in his fourth start for Kansas City, turned in his best outing of the season, tossing eight shutout innings as the Royals beat the White Sox, 2-1, at U.S. Cellular Field.
"That arguably could be the best-pitched game we had all year," Yost said afterward. "He was in total control."
Guthrie lasted only five innings in his Royals' debut on July 22, giving up five runs and walking three, while allowing six runs in 5 1/3 innings in his second start. He produced a quality start his last time out on Friday, allowing only three runs in six innings.
That steady improvement culminated in Wednesday's performance.
Guthrie, now 1-3 with a 5.18 ERA as a Royal, allowed only two runners to reach second base -- one on a sixth-inning double by Gordon Beckham and the other in the third, when Alejandro De Aza singled and advanced to second on an error by first baseman Eric Hosmer, who failed to handle Salvador Perez's snap throw from behind the plate.
Four of the five hits Guthrie allowed were singles, one of which -- De Aza's in the first -- was originally scored an error on shortstop Alcides Escobar.
Guthrie also struck out six and walked none -- just the third time this season he didn't issue a free pass in a start. One of the other instances was in his second start with the Royals on July 27.
"You're not going to talk to anyone who knows baseball that says he doesn't have good stuff. He's got great stuff," White Sox first baseman Adam Dunn said. "But usually it seems like you're going to get a pitch or two to hit. Tonight we did, but we didn't do anything with them. He didn't make mistakes."
It was Guthrie's first win since May 31. He went 0-9 with a 7.43 ERA in 14 games (10 starts) between victories.
"You want to win but you can't really make it happen, no matter how much you worry about it," Guthrie said. "All you can do is try to make better pitches and try to limit your runs. ... I think that was more the focus than getting the win, is can I go out there and give us a good outing that gives us a chance to win?
"Tonight's the first time I was able to go out there and keep a lead and pitch with the lead, and give us a chance."
Guthrie was backed with a pair of solo home runs by Mike Moustakas and Perez. Moustakas' shot, his 17th, came in the second inning, while Perez hit his sixth homer of the season in the fourth.
Both homers came with two outs.
Closer Greg Holland surrendered an RBI single to A.J. Pierzynski in the ninth before notching his third consecutive save.
Other than that, White Sox left-hander Jose Quintana (4-2, 2.78) was nearly as dominant as Guthrie, allowing only three other hits in seven-plus innings. Two of those hits were by Jeff Francoeur, who is hitting .438 (7-for-16) with two homers in his last four games.
Quintana also struck out five and walked two.
"He's been throwing the ball good for them and we had to get to him early," said Moustakas, whose last homer also came against Quintana on July 13.
The win gave the Royals their first road series victory since also taking two of three in Houston on June 18-20. Since that trip they had lost series in Minnesota, Detroit, Anaheim and Seattle, while splitting four games in Toronto.
It also was Kansas City's sixth win in its last nine games.
"We've been playing pretty good baseball here since August started," Yost said. "We had a horrible July, but we've rebounded, turned it around, and we're playing pretty darn good baseball right now."