Rashford, who delivered an assist in Barcelona's 6-0 win over Valencia on Sunday, has caught the eye of his German coach since joining the team from Manchester United.

"I've been following Marcus (Rashford) since he started with Manchester United," Flick said at Wednesday's press conference in Newcastle. "And I've always said, 'Wow, what a player he is!'"

"He has speed, but also in one-on-one situations, it's really impressive. And his finishing is unbelievable," Flick added.

"What I saw from him in the first weeks here is very good. And I think he still has potential to show us more," Flick said, expressing his confidence in Rashford's abilities.

Lamine Yamal, who started the season strongly with two goals and two assists in LaLiga, will miss Thursday's clash due to a hip injury on international duty with Spain. He may also be doubtful for Sunday's match against Getafe.

Barcelona will also be without Alejandro Balde and Gavi, as well as long-term absentee Marc-Andre ter Stegen. However, Frenkie de Jong is available for selection.

Flick remains confident about his team's Champions League prospects despite facing stiff competition. "I'm not thinking about who the favourite is to win the Champions League this season," he said.

"There are some very good teams, mainly coming from the Premier League," Flick noted. "What we saw against Valencia was very positive. We're playing well in all areas, and with this confidence, it's essential to play tomorrow."

Newcastle will be a tough opponent, but Flick is optimistic about his team's chances. "They are very strong, but we're confident," he said.