The teenager trained separately from the rest of the squad on Saturday after picking up a knock, but Flick was quick to downplay any suggestion of a serious issue.
"He trained separately. He's fine. He only had a knock," the Barcelona head coach said. "He'll travel with us, but we'll see if he plays."
Flick also used his pre-match press conference to explain the club's unusual system for choosing captains this season, under which he personally selects two of the five armband-wearers while the players themselves vote for the remaining three.
"We've been here three years and we know what the dressing room is like. I chose two, Raphinha and Pedri, and then the players chose three: Eric, Frenkie and Lamine," he said, noting that Marc-AndrĂ© ter Stegen and Ronald AraĂșjo had dropped out of the leadership group compared with last season. "It's been a good choice of captains."
The German also had warm words for Real Madrid despite their weekend defeat to Real Betis.
"I saw yesterday's game, Real Madrid played well. They had chances. This is football and it can happen," Flick said. "We want to have our own style. It will be a difficult match, we have to be prepared. It's not always easy to win."
On Gabriel Jesus, who has returned from a long-term injury lay-off, Flick struck an encouraging tone without rushing the Brazilian back to full fitness.
"I've enjoyed what I've seen of him in training. He's not ready to play at 100 per cent, but he could get minutes in the second half," he said. "I like what I've seen from him, with the ball, calm, facing goal."
Asked about Barcelona's spending in the transfer market, Flick defended the club's approach after a summer of significant outgoings from the academy.
"Deco and I decided this together. I'm happy. After the departures, you have to sign players," he said. "It's not easy for me to see Masia players leave and tell them to go elsewhere to improve. I know their dream is to play for Barça, but we have to be honest, and we want to win titles. We are Barça."
On Jules Koundé's willingness to play at centre-back, Flick praised the Frenchman's professionalism.
"What I can say about him is that he's an incredible professional. He gives everything. He's competitive," Flick said. "I spoke to him about the option of playing centre-back, and he prefers it. We want to help him reach his best level."