Historically, it is possible to meet in qualifying. In 2005, after the miracle in Istanbul, Liverpool was allowed to participate in the Champions League next year with a wild card, but from the first round of qualifying, it did not shy away from the principle of the same country. Fortunately, Liverpool signed a good contract in the third qualifying round, avoiding the northwest derby or Merseyside derby in the qualifying round (Manchester United in the third place in the Premier League played Everton in the fourth place). However, I met Chelsea in the group stage. The Red Army and Blue Bridge, two old enemies, tied in both group matches and joined hands to qualify. This is also the only time in the history of the Champions League to meet a league team in the group stage (the first round of the group stage). As a result, both teams failed, and Liverpool was defeated by Benfica. Chelsea lost to Barcelona because of the controversial penalty.
At present, the qualifiers, group matches and 16 matches all have the principle of avoiding the same country (league), and the top 8 matches can meet.