Strop was selected as a replacement player by the Cubs on Monday.
The unusual designation means Strop can be removed from the 40-man roster without passing through waivers. He's needed on an emergency basis with the Cubs placing three relievers on the COVID-19 injured list Monday. The 35-year-old had several good seasons for the Cubs in the middle of the last decade, but he's struggled to a 4.91 ERA over the last two seasons.