Pioli's wards failed to score points in the away match.
Milan in the match of the 22nd round of the Italian championship went to visit La Spezia and was defeated with a score of 0: 2.
Stefano Pioli's team were conceded early in the second half and were desperate to restore parity, but Bastogne's goal later made the task even more difficult.
La Spezia - Milan 2: 0 Goals: Maggiore, 56, Bastogne, 67 Spice: Providel - Bastogne, Erlic, Ismaili, Vignali - Ricci, Maggiore (Acampora, 83), Agudelo - Saponara - Jasi, Estevez.
Milan: Donnarumma - Teo, Romagnoli, Chjaer (Tomori, 64), Dalot - Kessier, Chalhanoglu (Heuge, 83), Salemakers (Castillejo, 83), Bennasser (Meite, 65) - Ibrahimovic, Rafael Leau (Mandjukic, 64).
Warnings: Vignali, Bastogne, Erlich - Dalot.