That will happen if Napoli beat Arsenal and Dortmund beat Marseille on matchday six on December 11.
Put simply, Arsenal must avoid a three-goal defeat in Naples to go into the last 16. For more details, read on.
According to Uefa's rules, if three teams end the group on the same number of points, the following 'tiebreakers' will be used (in order) to decide who progresses to the knockout stages:
(a) highest number of points obtained in the group matches played among the teams in question (Arsenal, Napoli and Dortmund)
(b) superior goal difference from the group matches played among the teams in question (ie. Arsenal, Napoli and Dortmund)
(c) higher number of goals scored in the group matches played among the teams in question (ie. Arsenal, Napoli and Dortmund)
(d) higher number of goals scored away from home in the group matches played among the teams in question (ie. Arsenal, Napoli and Dortmund)
If, after applying criteria (a) to (d) to all three teams, two teams still have an equal ranking, criteria (a) to (b) are reapplied exclusively to the matches between the two teams in question to determine their final rankings.
If this procedure does not lead to a decision, criteria (e) to (g) apply;
(e) superior goal difference from all group matches played;
(f) higher number of goals scored from all group matches played;
(g) higher number of coefficient points accumulated by the club in question, as well as its association, over the previous five seasons.

AllGood:

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