Mattingly said the club has been talking about making a change at closer for "about a week."
Jansen has converted two of three save chances this season, with a 2.53 ERA through 32 appearances. League has a 6.00 ERA, the highest among the Dodgers' active pitchers.
"You really would like a settling feeling when you get to that ninth inning. You would like to know the game is over," Mattingly said. "Losses like last night really hurt you."
Jansen had primarily pitched the eighth inning. Now Mattingly must find a way to get the right-hander the ball in the ninth with a lead. "I don't know that it works better this way," the manager said. "I wish I could say we had the sixth through the ninth covered. We'll just try to piece it together as best we can."
League will have a new role, though Mattingly said he's not quite sure what it will be.
"He wants to do whatever to help the team to win games," Mattingly said. "He's versatile. He's pitched everywhere out of the 'pen. We'll try to get him going. We're going to need him."
Austin Laymance is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.