PITTSBURGH — Andrew McCutchen’s left knee is aching. His team is listing. The Pittsburgh Pirates’ star center fielder is only too aware of the correlation.

Following another empty 0-for-4 night in a 7-1 loss to Cincinnati on Tuesday that dropped the 2013 NL MVP’s average to .185 and extended Pittsburgh’s losing streak to four, McCutchen acknowledged that his typical slow start is becoming something more alarming.

“I take full responsibility for how we’re playing,” he said. “I know that I’m a big part of it and right now I’m just not where I need to be at the plate. Right now, it’s under mediocre right now. It’s bad and I know I’m better than that.”

There’s plenty of blame to go around in a lineup that has now left 46 runners on base during its four-game slide, including nine against Cincinnati rookie starter Michael Lorenzen and a trio of relievers. The Pirates left the bases loaded twice in the fourth and the ninth while losing for the sixth time in seven games.

Starling Marte’s solo home run in the second provided the entirety of the Pittsburgh offense. Not exactly the way to help out Jeff Locke (2-2), who struggled early before getting through seven innings, giving up four run on seven hits with two walks and five strikeouts.

“I don’t think there’s cause for concern or anybody stressing out or anything,” Locke said. “It’s still early. ... There’s no sense of urgency or anything like that, it’s a long season.”

True. The Pirates limped through the first month last season before roaring to a second straight playoff berth. The starting pitching has been outstanding so far. A little hitting could go a long way, and McCutchen knows it.

“I’m going to do whatever it takes to get back to do what I know I’m capable of, being the player I know I’m capable of being,” McCutchen said. “Right now, I’m not being that player.”

McCutchen’s night at the plate included a grounder to short, a liner to right and two harmless pop ups. Manager Clint Hurdle admitted there’s a “disconnect” between the upper half and the lower half of McCutchen’s body, but is trying to remain optimistic. McCutchen tends to heat up as the mercury rises in May and June.

“He’s working, he’s trying to get better,” Hurdle said. “He’s trying to get things fixed as well.”

Marlon Byrd homered and drove in four runs for the Reds. Todd Frazier belted his National League-leading ninth home run for Cincinnati while rookie Michael Lorenzen (1-1) worked six-plus innings for his first major league victory. The 23-year-old righty kept the struggling Pirates off balance, giving up one run and three hits, walking three and striking out four.

“We missed some pitches we probably had to hit tonight,” Hurdle said.

The Pirates did manage to work seven walks in the game.