Semi-final qualification scenarios for the 2021 Intesa Sanpaolo Next Gen ATP Finals are as follows.

Singles Group A qualification scenarios after the completion of the second round of the event's group stage:

- Carlos Alcaraz has qualified for the semi-finals.
- The winner of Nakashima vs Rune will qualify as the #2 in Group A 

Singles Group B qualification scenarios after the completion of the second round of the event's group stage:

- If Korda defeats Musetti and Gaston defeats Baez, Korda will win the group and Gaston will qualify as the #2
- If Korda defeats Musetti and Baez defeats Gaston, Korda will win the group and Baez will qualify as the #2
- If Musetti defeats Korda and Gaston defeats Baez, Musetti will win the group and Korda will qualify as the #2
- If Musetti defeats Korda in three  or four sets and Baez defeats Gaston in three sets, Baez will win the group and Musetti will qualify as the #2
- If Musetti defeats Korda in five sets and Baez defeats Gaston, Korda will win the group and Baez will qualify as the #2
- If Musetti defeats Korda in three sets and Baez defeats Gaston in four or five sets -> Musetti will win the group and Korda will qualify as the #2
- If Musetti defeats Korda in four sets and Baez defeats Gaston in four or five sets -> Korda will win the group and Baez will qualify as the #2