(CNN) -- If Tiger Woods fails in his double bid to retain the Bay Hill title and regain his world No. 1 ranking this weekend, then it's a fair bet he'll be ruing his late lapses on the opening two days.
The 14-time major winner surrendered two strokes at the last two holes on Thursday, and lost three at the final three on Friday to be four off the lead at the Arnold Palmer Invitational.
"I played way better than what I scored today," Woods said on the PGA Tour website. "I missed a couple of short ones, and I had a rough finish."
It was another frustrating finish for the 37-year-old, who started the tournament in high spirits after publicly acknowledging his relationship with skiing star Lindsey Vonn.
He last held the No. 1 ranking in late October 2010, having occupied it for 281 weeks before a marital scandal that ended in in his divorce.
Added to injury problems, he dropped as low as 58th in the standings before resurrecting his career with three titles last year and two more this season.
Woods started the second round with a promising birdie and then eagled the par-five sixth hole before picking up further shots at 11 and 13.
However, it all went wrong as he bogeyed 16, 17 and 18 to drop to a tie for seventh place on five-under-par 139, having carded 70 after his opening 69.
"The good news is we've got 36 holes to go," said Woods, who seeking to join Sam Snead as the only player to win the same tournament eight times. "Certainly four shots can be made up.
"I've made my share of mistakes on the last few holes the last couple days. I need to clean that up."
Alongside him were fellow former world No. 1 Vijay Singh and fellow American Mark Wilson, who both moved up from 15th overnight with their 68s.
Bill Haas joined overnight leader Justin Rose at the top, with both on 135 after shooting 66 and 70 respectively.
Englishman Rose dropped a shot at his final hole, while American Haas had earlier finished strongly with an eagle at 16 -- emulating Woods' opening-day effort.
Haas, whose wife is due to deliver their first child in two months, is battling neck pain he suffered reaching down to pick up a towel at the Northern Trust Open.
"We should call it a sore neck, not an injury. When you're playing poorly, it hurts, and when you're playing well, it doesn't hurt," he said.
John Huh, born in New York to South Korean parents, dropped to third on 136 after a 69, while fellow U.S. players Ken Duke, J.J Henry and Jimmy Walker were tied for fourth on 138.
Major champions Ernie Els, Phil Mickelson, Webb Simpson, Lucas Glover and Trevor Immelman all missed the halfway cut along with FedEx Cup series leader Brandt Snedeker.
Mickelson, who will be seeking his fourth Green Jacket at Augusta next month, shot his worst round at Bay Hill -- 79 -- as he battles to regain the form he showed in winning at Phoenix last month.
"From where it was a few months ago, where I felt so good and my ball-striking was some of the best I've ever had, it is a little surprising," the 42-year-old lefthander said.
It was Snedeker's first start in a month following a rib injury, and he struggled with successive 76s.