Jake Arrieta is not happy about Philadelphia's scoring only one run against the Giants and points to the team's struggles while shifting on defense. (0:41)

The Philadelphia Phillies have lost six of their past eight games. And after a sweep at the hands of the San Francisco Giants, pitcher Jake Arrieta has reached a boiling point.

"Overall, it's just a really horses--- series," Arrieta said after the Phillies' 6-1 loss on Sunday. "Really bad. Really bad."

Sunday's loss featured the team's only run scored of the entire series, one driven in by Arrieta with a solo homer in the third inning.

The sixth home run of Arrieta's career wasn't enough to calm down the right-hander, who is in his first year with Philadelphia.

"We've had bad defensive shifts. We had a checked swing. [Shortstop Scott] Kingery should've gone to second on that play. And they got three hits in a row. The home run -- credit [Andrew] McCutchen for putting a good swing on it, but did not expect a ball like that to get out," Arrieta said in recounting how a five-run sixth inning for the Giants came together against him.

Arrieta got more specific on the topic of what he sees as defensive deficiencies.

"We're the worst in the league with shifts, so we need to change that," Arrieta said.

Arrieta added that accountability has also become an issue for the team.

"We need to have an accountability check," he said. "This is a key moment in our season. We had a pretty good April, a pretty good May. June isn't starting out so well."

Despite calling out his coaching staff's defensive decisions and a mistake from Kingery, a rookie, Arrieta said he hopes the team "can do something on the off day to get us back in the right mindset."

Philadelphia (31-26) begins a road series Tuesday against the Chicago Cubs, the team Arrieta left in free agency. Arrieta (5-3, 2.66 ERA) is not expected to pitch in that series as his next scheduled start is Saturday at home against Milwaukee.