Atletico won their first La Liga title since 1995 last term, while they also reached the semi-finals of the Copa del Rey and final of the Champions League.
However, Diego Simeone's rivals, in Spain and in Europe, have strengthened this summer and Garcia has called on each member of the team to "contribute" in the coming season.
"We always say that we know how we play and how we are working in order to arrive at the start of the season in good shape," Garcia told reporters.
"It's about working and helping the team. Each year there is a new season, with new players and we all need to contribute what we have."
Garcia scored nine league goals for Atletico last season.