Fati has been sidelined with a hamstring injury sustained in the 3-3 draw against Celta Vigo but is closing in on a return to first-team action.
The 19-year-old was spotted heading into training on Tuesday despite the players having been given a couple of days off after the win over Villarreal.
Fati is said to be doing everything he can to be able to play in the match and there is “moderate optimism” at the club that he will be ready in time, according to Diario Sport.
However, the striker still has to “prove himself” with the group. The players return to training on Wednesday to start preparations for the visit of Real Betis at the weekend.
The report reckons that Xavi will only use Ansu “if he is one hundred percent and will not take risks” with the youngster.
Xavi spoke about Ansu’s fitness in his presser before the Villarreal match.
“He is doing very well, he has very good feelings. He has started to run, but we have to be careful. Then we will see if we can take the risk or not,” he said. “The other day we did it with Ousmane, he did not score but he was close and that is appreciated. Ansu is a very important player and we cannot risk losing him again, but it will depend on the player’s feelings.”
Barcelona will hope the youngster is available as a win is likely to be needed in Munich if the Catalans are to progress to the last 16. Ansu has four goals in eight appearances this season.