The continued problems have left manager Mike Matheny searching for answers.
"We know that this is a talented group that can make [those plays]," Matheny said. "Just more inconsistency than what we would like."
The Cardinals added to their Major League-leading list of 69 errors when Siegrist made an errant pickoff throw to first base in the eighth inning. That allowed Ichiro Suzuki to get into scoring position, and Martin Prado drove him in to tie the score at 6.
Piscotty might have had a chance to nail Suzuki at the plate had he fielded the ball cleanly in right field.
"He throws the ball quick, and he's accurate," Matheny said. "I think we had a good shot."
Marcell Ozuna doubled to lead off the ninth inning after a ball sailed over Grichuk's head. Grichuk misread the ball, although it looked for a moment as though he had comfortably camped under it. Ozuna would eventually score, just as he did in the fourth inning, when Holliday couldn't pick a double-play ball out of the dirt.
A number of players are manning unfamiliar spots due to injuries. Grichuk batted leadoff and Holliday played first base as Matheny tries to find the right mix with Brandon Moss and Matt Carpenter on the disabled list. In addition, Siegrist was making his first appearance since returning from a bout with mono.
"I think we're trying to get creative to work on everything we can defensively, whether it's outfielders hitting their cutoff men or throwing to bases," Matheny said. "We're doing that a lot. Guys are getting plenty of work on the infield, probably as much as anybody else in the league."
Rosenthal allowed two inherited runners to score in the seventh and has now given up runs in seven of his last 15 appearances.
"I think he gets it," Matheny said of hearing the fans boo Rosenthal. "It's never easy to watch someone go through that or watch someone on your team go through that. Knowing that he's been taking good steps forward and today just wasn't one of them. Unfortunately, it has happened at home a few times [to the point] where the fans are going to respond how they're going to respond. It's just something he's going to have to work his way through."
This was the Cardinals' sixth loss when they were tied or leading after eight innings, and sixth in the first game of a homestand.
"It's just one of those things where we have to keep putting our head down and keep playing and demand from ourselves that it gets better all the way across," Matheny said. "Just cleaner baseball, whether it's pickoffs or coming up making throws or cleaner plays on the infield."