The win was the Pirates' second in a row and their third in four games. Of their 28 wins this season, half have been by a one-run margin. They are 14-12 in one-run games on the year.
McCutchen tossed 78 pitches, 51 for strikes, and got ahead of 12 of the 23 batters he faced, something manager John Russell stressed beforehand.
"I've been feeling good, and in Indy pitching, I just tried to do the same thing," said McCutchen, who was called up from Triple-A Indianapolis on Saturday. "I tried to stay ahead in the count and be able to use my offspeed [pitches], and it worked for me tonight."
The Pirates have gotten the win from their starter in each of their last three victories, this after the starters won just three times in a 35-game span from May 20 through last Saturday. Bucs starting pitchers have given up just four earned runs in their last 35 innings.
"They've thrown well -- that's the key," Russell said. "We're not scoring a ton of runs. We're starting to swing the bats a little better. ... Scoring a couple big runs tonight, I think these guys are starting to relax a little bit and hopefully we can continue that on."
Despite striking out eight times against Phillies southpaw Cole Hamels, the Pirates strung together three runs off the left-hander.
They scored a single run in the second, third and fourth innings, stranding runners at the corners in both the second and third.
A change Russell made near the top of the order paid dividends early. Pedro Alvarez, batting second for the first time in his 15-game Major League career, was just feet shy of his first career home run in the third inning, as his drive to left-center one-hopped the wall for a double and brought home fellow rookie Jose Tabata to give the Pirates a 2-1 lead.
Alvarez struck out twice to bring his early career total to 24 in 50 at-bats, but he has started to come along, having hit safely in four consecutive games.
"It's what I'm working for," Alvarez said. "It's what I'm trying to achieve. Still got a long ways to go. Just trying to feel more comfortable every day as the season goes on."
Tabata, the man hitting in front of Alvarez, suffered a scare an inning later when he was caught stealing. Phillies shortstop Jimmy Rollins accidentally stepped on Tabata's left hand while making the tag on the outside part of second base, but Tabata remained in the game after being looked at by several coaches and trainers.
After the game, Tabata had cuts on his ring finger, his pinky finger and the top of his hand, and he said that he felt some of the pain swinging in his last at-bat, three innings later.
"Tomorrow, I think I'll be OK," he said.
Wilson Valdez had tied the game at 1 in the third with a shot to left-center similar to Alvarez's, this one going over the wall for a home run off McCutchen. The 88-mph fastball on a 2-1 pitch proved to be McCutchen's only real mistake of the night. The right-hander was removed with one out in the sixth after Alvarez committed a fielding error on a Jayson Werth grounder.
"We were about to get him, I think," Phillies outfielder Shane Victorino said. "I think he was on the ropes. That's why [Russell] went and got him. I mean, he pitched well. I'm not taking anything away from the guy, but Russell probably felt like we were on the verge of getting him. That's why he came out and took him out after  pitches, unless he was on a pitch count. Early on, he definitely used his changeup effectively."
Russell said the situation called for the bullpen, which has carried the Pirates much of the year.
Never was that more evident than in the eighth inning, when Evan Meek struck out Ryan Howard on a full-count curveball with Rollins, the tying run, at second. Meek induced a Raul Ibanez flyout to left two batters later to complete his two scoreless innings and hand the ball to Octavio Dotel, who closed the door in the ninth for his 17th save.
Meek lowered his ERA back below one, as it now stands at 0.98. Russell said afterward that the right-hander deserves a spot on the National League All-Star team, something Meek said is rarely on his mind.
"A few people have asked me about it, and I thought a little bit about it," Meek said. "I think it would be an honor to go. It would be awesome to go. But other than that, I'm just trying to keep things day to day, just looking at the schedule, seeing what road trips we got, where we're going and just going from there. But in terms of thinking about it, I really haven't that much."