Brian Duensing, to be charitable, has had a bad run lately. In June, he posted a 17.28 ERA and 3.000 (!) WHIP with nine walks in eight innings.
He's getting some time off:
Dillon Maples has had some big league success, and in his last stint with the Cubs, last week against the Dodgers, he threw two scoreless innings and struck out three. He did walk two, and walks have always been his issue.
But Maples throws hard and if he can harness his command, he can be a successful reliever at the big league level.