‘‘One of the things that’s different from last year to this year — and we used this with MLB, as well as the city and state — is now we have some experience with outdoor events,’’ Cubs president of business operations Crane Kenney told the Sun-Times. ‘‘Last year, we were trying to convince [MLB] or the city and state to let us reopen during the season. We didn’t have any experience with this, and I think that was somewhat concerning to everyone.’’ ‘‘This plan was many months in the making, and it really has revolved around understanding the science of transmission of this disease,’’ said Dr. Robert Citronberg, an infectious-disease specialist affiliated with Lutheran General Hospital. ‘‘Knowing what we know about how far the virus can travel, where it lands, the effects that masks have on reducing the spread of the virus, we were able to draft a plan that really is completely science-based.’’