In a three-batter, 10-pitch span early Friday night, Jonathan Pettibone was, in a word, bad. He gave up a two-out double and two walks for an inauspicious beginning to his third start for Triple-A Lehigh Valley. Then, pitching coach Rod Nichols emerged from the dugout.

"He settled me down," Pettibone said. "He gave me a little breather and told me, 'Throw changeups to get this next guy. You'll get a groundout.'"

So Pettibone tossed an 0-2 change to Syracuse's Zach Walters and, sure enough, the switch-hitting shortstop hit a comebacker to the mound.

From then on, the Phillies' No. 11 prospect made change a constant and pitched seven dominant innings in the IronPigs' 6-0 blanking of the visiting Chiefs.

"The last couple outings, most of the hitters [I have faced] have been right-handed, so I have shied way from it," Pettibone said of his off-speed offering. "This lineup was more lefty-dominated, so I went back to it."

Pettibone (2-0) gave up only two hits -- Corey Brown's double in the first and single in the third -- while walking four and fanning two. He retired 13 of his final 14 batters and recorded 15 outs on the infield. His changeup, which dives down and away from lefties like Walters, was the key to his success.

"[My] changeup was working real well," the 22-year-old right-hander said. "Got a bunch of groundouts and my defense was good. I let them do the rest of the work."

Pettibone also allowed his batterymate to contribute. Catcher Sebastian Valle, Philadelphia's No. 8 prospect, slugged a three-run homer in the sixth and recorded a game-high four RBIs. Valle also homered in and caught Pettibone in his win over Pawtucket on Saturday. Both players were promoted from Double-A in the same week.

"Throwing to him in Reading, really ever since I signed," the 2008 third-round pick said of Valle, who is 3-for-22 in his first six games at Triple-A. "We have gone up to the same level together, and it's only a benefit. The last two, we have been on same page."

Pettibone has a 2.50 ERA in three games in the International League after going 9-7 with a 3.30 ERA in 19 outings for the R-Phils.

"Do no more than I have to," he said of his mind-set down the stretch. "With four or five starts left, the biggest thing is staying healthy, putting up innings. I have the same game plan."

Chiefs starter Tanner Roark (6-14) was charged with six runs -- three earned -- on eight hits over six innings. He struck out seven.