The outcome in Naples left second-place Roma 14 points behind league leaders Juventus with 11 games remaining, although the Giallorossi have a game in hand.
"It's a big gap," Garcia said to Gazzetta dello Sport. "We just have to look ahead and focus on finishing second in the standings."
Garcia felt his side would have been deserving winners considering the performance they produced at Napoli.
"This was our best game away from home this season," he said. "But football is a sport in which not necessarily the strongest team wins.
"We needed more luck and we had our chances to score.
"In any case to have seen my side play with such maturity and personality, having lost 3-0 at Napoli in the Coppa Italia (earlier this year), gives me confidence for the future."
Sunday's loss was only Roma's second of the campaign and allowed third-place Napoli to move just three points behind the Romans.
"The battle to finish second is wide open," Garcia said. "We are still second and we have a game in hand.
"What is important is that we remain focused and return to winning ways against Udinese."
Roma host Udinese on March 17 and hope to have Holland midfielder Kevin Strootman available in time for the match.
Strootman hurt his left knee against Napoli and will undergo tests on Monday to confirm the extent of the injury.
"The only thing that worries me is Strootman's injury," Garcia said. "His knee was swollen and that is not a good sign.
"We hope to get good news regarding Strootman this week."