Defending champion Se Ri Pak carded a 5-under 67 in the first round and is tied for second place with world No. 1 Annika Sorenstam, Donna Andrews, Jennifer Rosales and Mi Hyun Kim.
Michelle Wie, the amateur phenom who played in the PGA Tour's Sony Open in Hawaii this year, bogeyed her final hole, the ninth at Superstition Mountain, to polish off a round of even-par 72.
Saiki opened up on the back nine at the Prospector Course at Superstition Mountain and parred her first four holes. After that start, the 38-year-old drained a 25-footer for birdie at the 14th and holed one for birdie from about half that distance at the very next hole.
At the 167-yard, par-3 17th, Saiki knocked a 7-iron to 15 feet and cashed in on the birdie putt to make the turn at 3 under par.
Saiki wasted little time on the front nine. She hit a 9-iron to eight feet to set up birdie at the first and made it two in a row with a six-footer at the par-5 second hole.
Saiki continued her fine iron play at the fifth. She hit an 8-iron to six feet and ran home the birdie putt, then played a sand-wedge to tap-in range at the par-5 seventh for her seventh birdie of the round.
At the ninth hole, Saiki hit a 9-iron approach to 15 feet. She rolled in the birdie putt to place herself three clear of the field.
'It was just a solid round of golf today,' said Saiki, who is winless in 11 seasons on the LPGA Tour. 'I was very patient and everything just kind of flowed. I was basically in the zone today. This is by far the best ball-striking rounds of my career.'
Pak collected seven birdies and two bogeys in her opening round Thursday. She birdied two of her last three holes to get within three of the lead and put herself in better position for the title defense.
Sorenstam was more consistent than Pak Thursday. She started on the back nine and picked up back-to-back birdies at 13 and 14. Sorenstam dropped her only shot of the round at the par-4 16th but tallied four birdies on her second nine to grab her share of second place.
'Maybe it wasn't quite as tidy as I wish it would have been,' said Sorenstam. 'You know, 5 under, I'll take that any day, especially my first round out this year.'
Andrews, a six-time winner on tour but has not visited the winner's circle since 1998, birdied her first three holes. She birdied the seventh but three-putted from 40 feet for a bogey at No. 8.
Andrews rebounded with a birdie at the ninth, then sank a 30-footer for birdie at 16 to get into the clubhouse first at 5 under par.
'I made six birdies out there today, lipped out on the last hole for another one, and had a real consistent round,' said Andrews. 'I think keeping it in play off the tee is the key.'
Rosales mixed six birdies and a bogey for her 67, while Kim was flawless in her round.
Catherine Cartwright, Siew-Ai Lim, Lorie Kane and Catriona Matthew are knotted in seventh place at 4-under-par 68.