The teams announced the deal Monday.
Wisler was drafted by the Padres in the seventh round of the 2011 draft and was the top prospect traded to the Atlanta Braves for All-Star closer Craig Kimbrel in 2015. Cincinnati acquired him for Adam Duvall last July.
Wisler is 16-23 with a 5.14 ERA in 85 games, including 49 starts, in four big league seasons. He was designated for assignment by the Reds last week.
Lopez is a 22-year-old relief pitcher who pitched at three Class A levels in 2018. He had a 5.18 ERA in 31 games, striking out 53 in 41 2/3 innings.