“It’s not a move you want to make,” Mattingly said.
In his last five appearances, Guerra was 0-2 and has blown two of this three save opportunities. His earned-run average in that span was 13.50.
"I still have a lot of confidence," Guerra said. "Right now, we have to win ballgames. I’ll take the blame for five or six games. It’s my fault. I can’t blame anyone."
Mattingly said Guerra was understanding when he informed him of the decision earlier in the day.
Jansen is 2-0 with a 2.70 ERA in 16 appearances. He has 27 strikeouts in 16 2/3 innings, an average of 14.6 strikeouts per nine innings. Jansen averaged 16.1 strikeouts per nine innings last year to set an all-time major league record.