Meet the true X-factors in this World Series: The roofs

The World Series between the Milwaukee Brewers and Tampa Bay Rays could potentially be the first in Major League Baseball history played entirely indoors. With temperatures around 60 degrees expected in Milwaukee, American Family Field is likely to keep its retractable roof closed, while Tropicana Field in St. Petersburg is a permanent dome.

Both venues feature unique stadium ground rules regarding balls striking overhead structures, including roof trusses, cables, and catwalks. MLB officials, rather than the home team, will govern the roof status in Milwaukee during the postseason, while Tropicana Field has specific ground rules classifying catwalk impacts as either live balls, doubles, or automatic home runs.