What is the fine-grained topic of the following text: It was also the first game to feature a block containing teams which did not pertain to any of the main leagues (back then, it was known as "Rest of Europe" since all teams were European, the vast majority of them featured either in the 1998-99 season of the UEFA Cup or Champions League). Only return the topic.
First game to feature non-main league teams in UEFA Cup or Champions League