少し話題になっている18/19のCLですが、UEFA.comから引用すると
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UEFA CHAMPIONS LEAGUE
Group stage
There will now be 26 teams automatically qualified as per the access list drawn up from the UEFA association coefficients at the end of 2016/17.
For 2018/19 they will be ...
UEFA Champions League holders (1)
UEFA Europa League holders (1)
Top four from associations ranked 1st to 4th: Spain, Germany, England, Italy (16)
Top two from associations ranked 5th and 6th: France, Russia (4)
Champions of associations ranked 7th to 10th: Portugal, Ukraine, Belgium, Turkey (4)

If the UEFA Champions League holders have qualified for the group stage via their domestic championship, the vacancy will be filled by the champions of the association ranked 11th (Czech Republic), who otherwise compete in the champions path
If the UEFA Europa League holders have qualified for the group stage via their domestic championship, the vacancy will be filled by the third-placed club from the association ranked fifth (France), who otherwise compete in the league path
An association may have a maximum of five teams in the group stage
Qualifying
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とありますね。
今シーズンの４位までストレートインですね。