Florida - Tiger Woods took a step forward but acknowledged he had a lot of work ahead after Friday's second round of the Hero World Challenge where he trailed leader Jordan Spieth by 14 strokes.
Woods, back in competition after nearly four months away due to back injuries, improved to a two-under 70 after an opening 77 despite suffering from a fever, but a wobbly short game continued to plague him.
"It's not very good," conceded Woods, who stood last in the 18-man field. "Just going to take more time, more patience."
Not so for rising American Spieth, who scorched the back nine with five birdies including three in a row from the 12th to reach 11-under with one hole to finish when play was halted due to darkness after an 82-minute weather delay late in the round.
Spieth said the rain helped his birdie run.
"It was nice for us," he said. "The greens putted a little slower."
Australian Open winner Spieth held a two-shot lead over Sweden's Henrik Stenson, who posted a 68 despite back-to-back bogeys from the 15th.
Another shot back at eight-under were England's Justin Rose (64) and Patrick Reed, who played alongside fellow American Woods and went out in a sensational seven-under 29 on his way to a 63.
Woods came to the first tee with his grey shirt already drenched in sweat and coughed before several shots, but got through the front nine in even par and reached four-under for the day before a flubbed chip led to double bogey at the last.
The poor finish came right after the rain delay and washed away some of the gains of a back-nine stretch where Woods made eagle and two birdies in a span of four holes from the 13th.
Short game shortcomings hampered him again a day after flubbing three chips on his former home course of Isleworth.
The 14-times major winner, who is undergoing a swing change, also bladed a short chip some 60 feet past the hole at the eighth where he took a bogey.
Woods said it was all related to his swing changes, adding that two previous major swing revisions earlier in his career should help him.
"The good news is I understand the process," he said. "I've made changes before in my game and it takes time."Scores from Friday's second round of the Hero World Challenge at
Isleworth (USA unless noted, par 72, two players must finish round
Saturday due to darkness:
135 - Henrik Stenson 67-68
136 - Patrick Reed 73-63, Justin Rose (ENG) 72-64
137 - Jimmy Walker 68-69, Bubba Watson 69-68, Rickie Fowler 67-70
138 - Jason Day (AUS) 71-67, Keegan Bradley 72-66, Chris Kirk 70-68, Zach Johnson 67-71
139 - Matt Kuchar 69-70
141 - Hideki Matsuyama (JPN) 68-73, Graeme McDowell (NIR) 68-73
142 - Hunter Mahan 71-71
145 - Billy Horschel 73-72
147 - Tiger Woods 77-70
Players who must finish second round on Saturday:
Jordan Spieth 66
Steve Stricker 67