Belgian midfielder De Ketelaere, who joined from Club Brugge in the close season, came on as a substitute in their 4-2 win over Udinese and the 1-1 draw with Atalanta and Pioli said that the 21-year-old was ready to start at home on Saturday.
"In that role, I have many choices. Let's see from game to game... I trust him because he has great potential," Pioli told a news conference.
"He can be ready and play from the beginning, his time has perhaps come. He needs time. He has intelligence, and curiosity in understanding the movements and working methods."
Pioli said that either Olivier Giroud (35) or Divock Origi (27), who have been limited to substitute appearances for the champions in the league so far, could lead the line for the visit of Sinisa Mihajlovic's side.
"Tomorrow one of the two will be the starter," Pioli added. "Their condition is improving. From tomorrow, we'll play seven games in 21 days.
"I train a team of starters: they will all have to be ready and well prepared: it's time to start pushing."
Milan are fifth in the league table after two matches, two points behind early leaders Napoli, while Bologna are 12th.
