Only 15 players completed their rounds after torrential rain and thunderstorms had caused a three-hour delay to the start of the inaugural $7 million (£4.4m) European Tour event being played on the Mediterranean coast of Antalya.
The bad weather saturated the Montgomerie Maxx Royal course and made good scoring easy for the 78-man field, with only nine competitors over par.
Casey was seven-under through 14 holes when the players were called back to the clubhouse at 1642 local time (1442 UK time), the same mark as fellow Briton Steve Webster (12 holes) and South African Darren Fichardt (14).
World number one Woods, returning from a self-imposed break, is playing in his first strokeplay event for six weeks and showed signs of ring rustiness as he finished one-under through 10 holes.
The 14-times major champion found just two fairways all day and will have a 20-yard wedge shot over a greenside bunker awaiting him at the 11th when he returns to complete his round early on Friday morning.
"I thought when we teed off that we would be lucky to get in 11 holes and I was pretty spot on," Woods said.
"It just gets dark so quickly and it's like someone just turned off the light switch.
"The air is also heavy now with moisture so the ball is not going very far compared to when we were warming up on the range and early in the round. Towards the end we were hitting about a half-a-club short," added Woods.
"I'm still working on getting a bit of the rust out of my game but then tomorrow is going to be a long day for all of us."
The players were granted preferred lies due to the soaked conditions and Casey made a fast start with an eagle three at the first followed by birdies at the second and fourth.
The former Ryder Cup player, who ended a two and a half year wait for a European victory when he won the Irish Open in June, dropped a stroke at the fifth before producing another inspired run of four birdies in five holes from the ninth.
"It was a very aggressive start," said world number 97 Casey. "There are opportunities out there with two very reachable par-fives in the first four holes.
"I knocked a driver and three-wood on the green at the first and holed for an eagle. It was foot flat to the floor today and just fire at the pins, take advantage of the soft conditions and see what happens."
Woods spoke highly of the par-72 Colin Montgomerie-designed layout.
"It's a tricky golf course and it helps to have played it numerous times as it is one of those where you get a better feel for it the more you play it," said the 37-year-old American.
"Overall Colin's done a good job. Looking back on my 10 and a half holes I probably left a little out there ... so the goal in the holes I have left in the morning is to pick up a few quick birdies."
Woods played in a three-ball with money-list leader Henrik Stenson of Sweden and U.S. Open champion Justin Rose in the penultimate tournament of the season.
Stenson fared best of the three, finishing on four-under while Briton Rose was on the same one-under mark as Woods.
Dane Thorbjorn Olesen and Ricardo Gonzalez of Argentina went round in 66.
Also on six-under with holes remaining were Dane Thomas Bjorn, South African Justin Walters, Spain's Rafael Cabrera-Bello, Portuguese Ricardo Santos and American Peter Uihlein.
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