Lazio will start the match in fifth in Serie A on 31 points, but victory could see them finish the round third if Napoli and Sampdoria both fail to win.
Sampdoria host Palermo on Sunday, while Napoli will welcome Genoa to the Stadio San Paolo on Monday.
Lazio dropped to fifth last week when they lost 1-0 at home to Napoli but Mauricio - who signed for Stefano Pioli's side on loan from Sporting Lisbon on Wednesday - feels they are more than capable of reaching next season's Champions League.
Mauricio made 14 starts in the Portuguese Primeira Liga this season, and is confident he is ready to play against Milan just days after joining Lazio.
"I am a strong defender and I have a good speed. I am also suitable as a full-back," Mauricio said, in quotes reported by Corriere dello Sport.
"Physically I'm ready because I was training every day with Sporting Lisbon. On Saturday we will see with the coach."
Mauricio was one of two signings made by Lazio this week, with Wesley Hoedt also joining from AZ Alkmaar.
The 20-year-old Dutchman will not make the move to Rome until the end of the season, though.
Lazio entertain Milan having won six of their past eight matches in all competitions at the Stadio Olimpico, losing only to Napoli and Serie A leaders Juventus.
Milan, who sit eighth, have not won in five away league games and their coach Filippo Inzaghi - who could hand a debut to Suso, a January signing from Liverpool - is beginning to come under some pressure.
The 18-time Italian champions lost 1-0 at home to Atalanta last week and sit five points adrift of Lazio.
Inzaghi's team have taken just one point from their three Serie A fixtures since the end of the mid-season break.
