"She's amazing," Choi said Sunday after tying for second with Ai Miyazato. "She plays so well. She never looks nervous or if there's pressure on her. ...
"I don't know who can stop her right now. She hits it really far. Me and Ai, we tried our best, but she's pretty far away from us."
The 24-year-old Tseng won her 14th LPGA Tour title and second in four events this year. She led the tour last season with seven victories — including major wins in the LPGA Championship and Women's British Open — and finished with 12 worldwide titles.
On Sunday, Tseng overcame a three-stroke deficit for a one-stroke victory, fighting through rain, hail, cold, wind and lightning delays.
"British Open with cacti," her caddie, Jason Hamilton, said on the practice green minutes before the leaders teed off.
Tseng two-putted for par from 40 feet in fading light on the 18th green to hold off playing partners Choi and Miyazato.
"It was a little drama out there," Tseng said.
Tseng closed with a 4-under 68 to finish at 18 under. The second-ranked Choi also shot 68, and Miyazato had a 69. The three players are friends and all work with Scottsdale-based Pia Nilsson and Lynn Marriott, Annika Sorenstam's former instructors.
"We were so close," said Tseng, also a one-stroke winner over Miyazato last month in the LPGA Thailand. "It was very good. They both played very well."
Because of lightning near the Wildfire Golf Club, play was delayed three times for a total of three hours. Tseng holed her winning 2-foot putt at 6:45 p.m. — 8 hours, 4 minutes after the leaders teed off and seven minutes after sunset.
"I was feeling like we were going to finish tomorrow, so we were really lucky to finish today and finish in the dark the last few holes," Tseng said. "Because of my eyes, I couldn't see much of a distance, so I tried to keep to myself, 'OK, just finish these few holes, just hit a good shot, good contact, play one shot at a time.'"
After temperatures in the mid-80s Thursday and Friday and the high 70s Saturday, the mercury plunged into the low 40s Sunday morning and only got up to the mid-50s.
"It was definitely a long day, and I've never seen this weather in Phoenix before," Miyazato said. "Thank God we finished."
Following overnight rain, play began at 8:30 a.m. It was still in the mid-40s, spitting rain and windy when the leaders teed off at 10:41. Soon after, hail fell briefly on parts of the course.
"The weather was really tough," Tseng said.
Three strokes behind Miyazato at the turn, Tseng birdied five of the first six holes on the back nine and closed with three pars. On Thursday in the first round, she played a seven-hole stretch on the back nine in 7 under with an eagle and five birdies.
"I told myself, 'We have nine more holes, OK, three shots back. You still have a good chance on the back nine. Just play like on the first day, try to make birdie every hole,'" Tseng said. "I played 7 under here before, so maybe I can do it again. I played 5 under, so it was pretty close."
Tseng, tied for the third-round lead with Miyazato at 14 under, bogeyed the seventh and eighth holes to fall three strokes behind the Japanese player.
After the second delay, with the sun poking through the clouds, Tseng returned to hole a 25-foot birdie putt on the par-4 10th.
"I think was a good break for me because I finished nine holes, was 1 over and I had a birdie chance on No. 10," Tseng said. "I came back here to relax a little bit and rethink, restart the day. So, it was a good break for me."
She followed with a 6-footer on the par-5 11th to pull within a stroke, then made a 16-foot putt from the fringe on the par-4 13th to tie for the lead at 16 under.
Following the last delay, Tseng pulled ahead with a 20-foot birdie putt on the par-3 14th. Choi, from South Korea, also birdied the hole to tie Miyazato for second.
"I was really cold when I get back there," Tseng said. "My hands were like rock. I have no feel with my hands and tried to get warm, and it was just really tough."
Tseng opened a two-stroke lead with a birdie in heavy rain on the par-5 15th.
"I think 15 was really a key hole because if I made birdie on that hole, I think I still had a chance," Miyazato said. "But it rained so hard, and it was really cold, and my hands like didn't have a feeling, so it was really tough."
Miyazato and Choi birdied the par-4 16th to pull within a stroke, but could only match Tseng's pars on the final two holes as they raced to avoid a Monday finish.
On the 18th green in front of about 75 spectators, Tseng lagged her 40-foot birdie try back down the hill to 2 feet. Choi then came up 4 feet short on a 30-footer on a similar line, and Miyazato missed a 25-foot attempt from pin-high on the right side.
"It was a little bit dark to read my birdie putt, but it wasn't breaking much in the end," Miyazato said. "That's why I missed, but I think I had a good stroke."
Choi was simply relieved to finish and get out of the cold.
"It was so, like, long day, and then it was a really tough day," Choi said. "I'm really cold right now, so I can't speak. ... The weather was just so bad. Right now, I'm finished, so I'm very happy."