The condolence message was made public on Nottingham's website ahead of the quarter-final second leg at the City Ground.
"Elliot Anderson is unavailable for tonight's game following the passing of his beloved mother, Helen."
Nottingham won the match 1–0 and advanced 2–1 on aggregate. At the same time, Aston Villa beat Bologna 7–1 on aggregate. Victor Nilsson Lindelöf was on the Villa bench.
In one of the semi-finals, Villa will face Forest.
In the second, Freiburg and Braga meet. The Portuguese, with Gustaf Lagerbielke in the team, turned a 0–2 deficit into a 4–2 away win against Real Betis.
