PITTSBURGH — James McDonald’s fastball is losing velocity quickly. Maybe his health is the problem.

The St. Louis Cardinals roughed up McDonald in a 10-6 victory over the Pittsburgh Pirates on Monday night, chasing him after just 1 1-3 innings. He was charged with eight runs — three earned — during the shortest start of his career.

McDonald declined to talk about how he’s feeling, but the radar gun hints at trouble. The 28-year-old’s fastball typically hovers in the 93-94 mph range. He didn’t hit that number against the Cardinals, and St. Louis took advantage by pounding him early to end Pittsburgh’s three-game winning streak.

“You make mistakes, they’re going to make you pay,” McDonald said. “I didn’t keep my team in the game today. That’s what happens when you make bad pitches, you get hit hard.”

Jon Jay and Matt Holliday each had two hits and two RBIs. Allen Craig doubled and drove in three runs for the Cardinals, who took command after scoring seven runs in the second.

McDonald was met with a chorus of boos as he handed the ball to Clint Hurdle. The manager refused to speculate about McDonald’s health but allowed that the right-hander is not the same pitcher who was one of the National League’s best starters in the first half of the 2012 season.

“There wasn’t anything real crisp,” Hurdle said. “He just couldn’t get the ball where he wanted it, couldn’t repeat it and it was hard. ... Too many pitches up and over the plate to a good-hitting team.”

Starling Marte had three hits and Neil Walker homered for the Pirates, who couldn’t quite duplicate their stirring comeback win over Cincinnati on Sunday. Pittsburgh spotted the Reds a 5-0 lead before rallying for a 10-7 triumph.

The Pirates pulled within four in the eighth and had two runners on, but Travis Snider and Andrew McCutchen both grounded out to end the threat.

“We had the tying run on deck after being down 10-1,” Hurdle said. “I like the way we’re playing. The hiccups we’ve had off the mound have been challenging but we’ve been able to handle them so far.”

Lance Lynn (2-0) labored through five innings to get the win. Lynn allowed four runs, walking three and striking out four.

McDonald began the season hoping to recapture the form he showed in the first half of 2012, when he nearly made the All-Star team. He pitched well in his first start and then overcame a shaky first inning in Arizona last week — when he allowed four runs before getting three outs — to pick up the win.