With a win enough for Feyenoord to clinch a second-place finish, Robin van Persie started with full-back Jordan Bos as his left winger and right-back Jordan Lotomba as his left-back, leaving Raheem Sterling and Gijs Smal on the bench.
AZ opened the scoring in the same stadium that saw them win the KNVB Beker just three weeks ago - sloppy play at the back handed the ball to AZ deep in Feyenoord's half. Troy Parrott was put one-on-one by Jordy Clasie and whipped it over Wellenreuther, giving the visitors the lead in the opening minute.
Somehow, Anis Hadj Moussa failed to equalise for Feyenoord after being given a clear-cut chance by a sleeping Utrecht defence, with Rome-Jayden Owusu-Oduro saving a close-range effort and a wide-open Ayase Ueda being overlooked by Hadj Moussa, even though the top scorer stood a meter next to him.
The Algerian winger made up for his earlier mistake by scoring the equaliser just before the 60-minute mark, calmly placing the ball past Owusu-Oduro's near post after a delightful deep pass from Tobias van den Elshout.
A quiet end to the second half only saw Peer Koopmeiners test either goalkeeper, with the midfielder's long-distance attempts not enough to keep Feyenoord out of the Champions League.
Robin van Persie's team secured a spot in the League Phase of the 2026-27 UEFA Champions League with Sunday's draw, with their four-point lead enough to secure a second-place finish.
Meanwhile, AZ confirmed their spot in next year's UEFA Europa League, with a third-place finish now impossible for the Alkmaar side.