Fernando Rodney (5.68 ERA) latest roll of dice for Cubs' pen

SAN FRANCISCO – After their 9-1 loss to the Giants in Thursday’s series finale, the Cubs announced a trade to acquire another struggling, once-dominant relief pitcher.

Right-hander Fernando Rodney, who had a 5.68 ERA this season before the Mariners designated him for assignment this week, was acquired for a player to be named later or cash considerations.

The power pitcher just three years removed from setting a major-league relief-pitching record for ERA (0.60) with Joe Maddon’s Tampa Bay Rays is expected to join the Cubs’ bullpen Friday in Los Angeles.

“He’s got the kind of stuff to get out both righties and lefties,” said first-year Cubs manager Maddon. “I know he had trouble, struggled a bit this year. But I’m eager to see it in person and find out what’s going on.”

Rodney’s the second former Rays closer the Cubs acquired this summer, former All-Star Rafael Soriano, who was ineffective before going on the disabled list in early August because of shoulder inflammation. The Cubs also looked into acquiring former Rays closer Grant Balfour this season.

The move comes four days after the Cubs placed reliever Jason Motte (shoulder) on the disabled list, but Cubs manager Maddon said the trade was more about an ongoing effort to improve the Cubs’ iffy bullpen depth.

The bullpen has largely performed well overall this season, but it has been leaned on heavily in August, averaging more than three innings per game, with a 4.52 collective ERA for the month.

“We’ll see when we get him in here and get him in a game,” Maddon said. “But he still has a good baseball. He has an outstanding changeup. And he’s a great teammate; he’s a lot of fun to have on the team. So I’m looking forward to that.”

To make room on the 25-man roster, the Cubs optioned left-hander Zac Rosscup back to AAA Iowa. To make room on the 40-man roster, right-hander Brian Schlitter was designated for assignment.