"The offense was really not the problem. We got shots. We just didn't make them," said Parker, who declared himself fit after suffering a twisted left ankle and bruised left thigh in Game 1.
"It was defensively. We can't let them score 107. We have to find ways to cut that number down."
The Spurs finished the regular season ranked third-best in the NBA in points allowed at 97.0 per game.
But the Spurs couldn't stop the Clippers, who shot 51.3% from the field, 55.6% (10 for 18) from three-point line, while getting 23 fast-break points. Blake Griffin also threw down several emphatic dunks.
"Defensively, we thought we were not very good," forward Tim Duncan said. "A lot of mistakes, a lot of transition points. A lot of turnovers that turned into points for them. So there are things that we can clean up."
On offense, the Spurs shot just 36.6% from the field, 30.3% from three-point range. But players said they had open looks, the shots just didn't fall.
Having a more healthy and in-sync Splitter on defense in Game 2 Wednesday night at Staples Center is what the Spurs are counting on.
Splitter played nine minutes, 57 seconds in the first game — his time split between the first and third quarters — and the center had four points and three rebounds.
Splitter missed the last six regular-season games with the calf injury.
"He didn't go backwards, so that's a good thing," Spurs Coach Gregg Popovich said. "Maybe he can play a few more minutes [Wednesday] night. I'm hoping."
Said Parker: "Tiago is a big piece of what we're doing. So hopefully he can play a little bit more tomorrow. We definitely need him."
As for Parker, his ankle and thigh are "a little bit better."
The two days off between games have helped the point guard.
"When I looked at the schedule, it was like, 'Aw, [the series is] going to be longer.' Now I'm very happy we have an extra day," Parker said. "That will definitely help tomorrow."