The Frenchman's side failed to take advantage of Juventus' draw at Hellas Verona, remaining nine points behind the Serie A leaders with a game in hand.
Garcia was happy with the way Roma kept the ball, but said they needed to be better in the attacking third.
"We took the initiative and kept possession, but to win games you need to be better in the final and penultimate passes," Garcia told Sky Sport Italia.
"This is what we lacked. It is an 'away' point and we have learned that it's not enough just to attack, as you must also be more determined in front of goal."
Both teams had half-chances at the Stadio Olimpico as Roma improved their remarkable defensive record in the league, now having conceded just 11 times in 22 matches.
Garcia was positive about the result, particularly pleased his team gave nothing away in the title race.
"Let's look at it on the positive side. We didn't lose ground on Juventus in the title race, we can say we drew an away match and a draw in any away game is never a bad result," he said.
"We gave it everything to win, and that's what I liked. Of course there's room for improvement in attack, as we saw tonight."
Garcia said the derby played out largely as he wanted with Roma giving Lazio few chances.
"We played the game as we wanted to play it, being careful with their counterattacks and we did a good job in defence as well, because Morgan De Sanctis didn't have to make any saves," he said.
"But, I repeat, we had to score the first goal, otherwise the game was always going to remain close, as it was until the last minute."
