McPherson gave up three runs in the third inning and the Baltimore Orioles beat the Pirates 6-3 at McKechnie Field.
With the score tied at 1, McPherson hit leadoff batter Alexi Casilla in the third and walked Ryan Flaherty. Jason Pridie hit a one-out RBI single, Travis Ishikawa doubled in a run and Trayvon Robinson drove in another with a single.
It was the third start of spring training for McPherson, the club's 2011 minor league pitcher of the year. He had hoped to go four innings but was lifted early when his pitch count jumped into the 50s. The 25-year-old right-hander faced 17 batters, including eight in the third.
"The pitch count was good going into the third inning, but with the three-spot in that inning it was a lot of hitters," McPherson said. "It's easy for that pitch count to jump up on you. After the third inning they decided to say that's good enough and just get ready for the next one."
Wei-Yin Chen allowed two runs, one earned, and one hit over 2 1/3 innings in his second start for Baltimore. He walked two and struck out four.
Baltimore's projected No. 2 starter said his slider still needs work, but he felt good about his two-seamer and four-seamer.
"I feel my delivery is much better than last outing," Chen said through a translator. "I feel my fastball got life."
Chen thinks he's right on schedule in his preparation for the season, and Orioles manager Buck Showalter agreed.
"He's in a good spot," Showalter said. "His arm feels good. He feels good physically, and I like where he is."
Pittsburgh totaled six hits, two by Starling Marte.
Marte, who will likely open the season batting leadoff, was 2 for 2 with a walk. He stole two bases and scored twice. He was also caught stealing once.
The 24-year-old outfielder made his major league debut on July 26 last season and hit .257 in 47 games.
"He's got the tools to be a very dynamic leadoff hitter," Pittsburgh manager Clint Hurdle said. "He's showing some maturity and a little slower heartbeat when he gets on base now. He's going to be a fun player to watch grow."
The Orioles signed 17 players to one-year contracts. The most notable were 3B Manny Machado, and RHPs Jake Arrieta, Miguel Gonzalez, Pedro Stop and Chris Tillman. All 40 players on their roster are now under contract. ... RF Nick Markakis, who hasn't played since he was scratched from last Sunday's game, won't play until later next week, Showalter said. ... RHP Dylan Bundy, the Orioles' first choice in the 2011 draft, makes his first start Saturday night against Boston in Fort Myers. He's scheduled to be followed by RHP Kevin Gausman, Baltimore's first pick in last year's draft. ... The crowd of 6,353 was the largest to see a night game at McKechnie Field. ... Pirates RHP Jeff Karstens (biceps) pitched two innings of batting practice in his progression back to the mound. ... 1B Garrett Jones (oblique) had limited physical activity a day after being scratched from the lineup. But he hopes to swing a bat Saturday.