Wandy Rodriguez has identified the issue that plagued him in his past two starts -- a small problem with big consequences.

One pitch that missed its location turned his start Thursday, just like it did in his previous outing. That pitch Thursday against Wil Nieves resulted in a home run that gave the Arizona Diamondbacks the lead and sent the Pirates to a 6-3 loss at PNC Park.

"I don't know what's going on with me," Rodriguez said. "I've lost two games, it's only been one pitch."

With the Pirates leading, 3-2, in the sixth and a man on first with two outs, Rodriguez hung a breaking ball to Nieves, who the Diamondbacks claimed off waivers Monday from the Colorado Rockies. Nieves turned on the high breaking ball and hit his second home run of the season, pushing the Diamondbacks ahead.