Ismael Bennacer (25) gave Milan a 1-0 home win over runaway Serie A leaders Napoli in the first leg last Wednesday.
It was Milan's second consecutive victory over Napoli after humiliating Luciano Spalletti's side 4-0 away earlier this month.
Nigerian Osimhen missed both matches with a thigh injury.
"He is such a powerful, impressive and decisive striker so we take his characteristics into account, but at the same time we have our own way of playing football and we won’t move away from that," Pioli told reporters on Monday.
"We saw with previous Napoli games that a lot of it is about knowing the moment to slow down and speed up, and that is even more crucial with a player like Osimhen.”
Pioli said a one-goal advantage was not enough to provide security against an aggressive Napoli side who have not lost at home in their last 12 Champions League games.
"We only have a minimal advantage. We need to play our game as a team and I think control the ball very well when we have it. That will be an important element," he said.
While Napoli will be without centre-back Kim Min-Jae (26), midfielder Andre Zambo Anguissa (27) and striker Giovanni Simeone (27), Pioli's only injury concern surrounds French forward Olivier Giroud (36), who has been dealing with Achilles issues.
"Giroud had a slight problem in training, but he has overcome it and is ready to play," Pioli said.
