The 20-year-old sealed a transfer deadline day (September 1) switch to the Blues for the 2025/26 season, with the Argentine expressing his excitement about the move and the prospect of playing in the Champions League.
"It’s a great step in my career. I’m really happy to be here and ready to offer as much as I can to the team and the staff. I’m sure it will be a positive season," he said.
"Of course, I’ll get the opportunity to play in the Champions League for the first time, which will be a great challenge. I’m really looking forward to this season and hopefully I can help the club to achieve its goals."
However, on Wednesday, Chelsea named their Champions League squad for the league phase of the tournament - and Buonanotte is not in it.
There are 17 slots available for players who don't count as homegrown, with teams allowed to name a total of 25 players. However, clubs must have trained four players in the same league and four players by the club itself.
Ergo, the Argentina international must wait until the knockout stages to fulfil this Champions League dream - with sides able to name updated squads for that phase of the competition, which starts in February.
Chelsea only named 24 players and not 25, as they left a club-trained space empty. The three club-trained players include academy products Reece James, Levi Colwill, and Trevoh Chalobah.
Buonanotte will hope he can impress in the Premier League and cup competitions before February to stand a chance of playing in this season's Champions League.