Riveiro was presented by AIK in January after former coach Mikkjal Thomassen was fired. The Spaniard coached AIK for just over a month, including during training camps abroad, before his new club's first competitive match on Sunday.
AIK then lost to Västerås, who will play in the Allsvenskan again next season after winning the Super League in 2025.
22-year-old Axel Taonsa opened the scoring for the away team after half an hour, and nine minutes later veteran Jonathan Ring added to make it 2–0.
In the second half, AIK looked for an equalizer but failed to score.
Häcken and Oddevold are also in AIK and Västerås' Swedish Cup group.
