The Rossoneri talisman returned to training on Wednesday afternoon.
After missing several weeks out due to injury, Bacca has finally rejoined full first team training. He had previously been on a separate, personalized recovery program at the Milan training ground.
According to Sky, Bacca is unlikely to start against Atalanta, but should be at least on the bench for the clash at the San Siro on Saturday.
Meanwhile, Bonaventura did not train with the rest of the group today, which places him again in doubt for the weekend fixture.