Messi's double saw Barcelona progress to the Copa del Rey quarter-finals and Garcia remains unsure how to stop the 26-year-old when he is full flow.
His second came after a mesmeric dribble through the Getafe defence, bursting through their backline before rounding goalkeeper Jordi Codina and slotting home.
The Argentina international has scored 10 goals in 14 appearances against Getafe during his career, with the latest two taking him to 18 goals this season.
Garcia asked after Thursday's match: "With a guy that scores so many goals, how do you stop him?
"It is a question I talk to other coaches about. He's hard to stop.
"When (Messi) gets started, he creates panic. You have to play the perfect game.
"We've not been too bad against Barca."
Garcia admitted he had not seen Messi's incredible second goal, because it happened too quickly.
"I haven't seen it, it was too fast," he added.
"He's done it against so many teams. People say you can stop him with fouls but you can't, he just keeps going."
