However, the 22-year-old Texan took comfort from the way he had rebounded in the second round, and pointed to his impressive form after three of his four missed cuts on the PGA Tour last season.
"I can certainly take positives out of today's round," Masters and U.S. Open champion Spieth told reporters after mixing eight birdies with five bogeys on a challenging Riviera layout. "I'm not going to let this one get to me very much.
"Did a lot of talking with (caddie) Michael (Greller) throughout the round today. He was just saying, 'You know, don't make this a bigger deal than it is.
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"Look at your missed cuts last year and what happened right after.' And he's right. We rebounded in a perfect form last year on just about every missed the cut. We'll be fine."
Last season, Spieth followed his first two missed cuts on the U.S. circuit with a tie for seventh and a runner-up spot.
He later missed successive cuts, at The Barclays and Deutsche Bank Championship, before tying for 13th at the BMW Championship and winning the season-ending Tour Championship.
Spieth was happy with his birdie count on Friday, but frustrated after an unfortunate bogey on his second hole of the day, the par-five 11th, and with his form on the closing stretch.
"Coming into the day, the hardest part is trying to make enough birdies, and I did that. Just too many mistakes," he said.
"Just the same thing as yesterday, some sloppy iron play," added Spieth, whose next PGA Tour event will be the March 3-6 WGC-Cadillac Championship at Doral.
"That needs to be fixed by some rest and some time away from my clubs for a few days. And then when I come back ... I just need to be out there on the range a little bit more than I have been leading up to events."
(Editing by Larry Fine)
