Bertrand has played over 150 first team games - but all away on-loan.
"Just to come on against Birmingham for my debut was a great bonus to begin with," Bertrand told chelseafc.com.
"It was a good moment for me personally but then to get the assist as well and the reaction of the players after that was pretty special. The crowd took to me as well so it was a brilliant all-round experience. I was really grateful for the crowd's reception."