Lazio moved into the top three with the 2-0 win.
“We suffered because in the first half, despite playing well, we didn't make that count by taking the lead," Pioli told Sky Sport Italia.
“When you don't make pressure count, it leaves your opponents the opportunity to get back into the game. We wanted this victory badly and got there with team spirit and character, so that is already an important development.
“We are lethal on the counter-attack, but struggle against sides that close up. As soon as they went close to a goal, we got scared and it gave them courage.
“We are also not accustomed to playing every three days, but we're getting good results in Serie A and Europe anyway.
“I have a young side and I'm happy with them, but at times young players can have gaps during a game when they lose concentration and intensity."