The teenager, linked with moves to Manchester United and Liverpool over the summer, made the switch from Benfica to Sporting Lisbon in a colossal €126m switch to become the fifth most expensive player of all time.
The European champions were one of several Premier League sides who scouted Felix during his Benfica days, but his transfer was ultimately deemed too costly and he instead made the move to the Spanish capital.
But now, as the youngster prepares for his first Anfield experience, the player has conceded that the Champions League pairing against the reigning European champions is “as hard as it gets” for his side.
Speaking to Eleven Sports, Felix said: “It will be a very difficult tie.
“Perhaps of all the teams, they are the most difficult team.
“Liverpool are in good shape, in excellent form, they are the defending champions and it will be very difficult, as with any match in the Champions League.
“But against this Liverpool who are doing very well, it will be even more difficult.”