The Cubs are traveling to Toronto to take on the Blue Jays and as per Canadian government rules, visitors to Canada must be vaccinated against COVID-19. (The United States has the same rule for non-citizen visitors to the USA.) Because of that, left-handed pitcher Justin Steele and right-hander Adrian Sampson will be placed on the restricted list and will not be making the trip.
While no official announcement has been made as of late Sunday night (when I wrote this) as to who will take the two pitchers’ places on the roster, multiple reports have said that left-handed reliever Brendon Little and right-handed reliever Jeremiah Estrada were with the team in Milwaukee on Sunday.