The 21-year-old goalkeeper kept a clean sheet for the Rossoneri in his first Serie A outing for the club, helping his side to a 1-0 win over Udinese on Saturday evening
Valter Birsa's first-half strike was enough to seal the points for the hosts but Gabriel had to be at his best to defend that lead, tipping an Antonio Di Natale free kick onto the crossbar after 64 minutes.
The young Brazilian, who was drafted into the side after fellow shot-stopper Christian Abbiati was ruled out with a calf injury, expressed his happiness at finally making a league appearance and the display he put in.
"It was a great debut for me and I am very happy," the former Cruzeiro man told Sky Sport Italia.
"Of course there's going to be a little tension at the start, as this was a difficult game we had to win. We slowly started to gain confidence and it went very well at the end."
"The coach had already warned me Di Natale took great free kicks and I had seen some of his games before," he said when asked about the excellent save he made from the Zebrette forward.
"When I saw it was his free kick, I expected him to go near post and thankfully I was able to get a hand to it."
Gabriel, who moved to San Siro from Brazil in 2012 and has one senior cap, will not continue in the side for Tuesday's Champions League clash with Barcelona having not been named in the European squad and refused to get carried away about his future.
"That is down to the coach and club," he said when asked whether he could be a Milan regular.
"I am working to grow and to learn, so good things will happen, such as this debut.
"When the Champions League list was drawn up, I was not 100 per cent due to a shoulder injury, so the coach made the right choice. Now I am fit, thank God."
The Rossoneri have moved to seventh in Serie A with the win with 11 points from eight games, overtaking Udinese, who sit in ninth.