Padraig Harrington lies just one shot off the early pace set by Jim Furyk after the first round of the Target World Challenge following a seven under-par 65.
Furyk, who had an eagle three at the second and six birdies to card a 64, is one shot ahead of Harrington and Nick Price, while Davis Love III is another stroke further back following a 66 in the elite event at Thousand Oaks in California.
Defending champion and tournament host Tiger Woods hit seven birdies in his round but a few mistakes meant he could only post a 68.
The world number one failed to get the start he wanted, making three bogeys in the first four holes with a birdie at the third. But Woods hit back with four consecutive birdies from the fifth, before picking up further shots at the 11th and 13th.
Colin Montgomerie also carded a 68 along with Phil Mickelson, one behind David Toms, Retief Goosen and Chris DiMarco.
The Scot predicted low scores in the remaining three rounds of competition.
"The greens are pure," he said. "There is no traffic on the greens, so there is no reason why people can't go low. "There are 12 of the top 15 golfers in the world here, so if they don't go low, no-one will."
The winner of this 72-hole event receives $1million. Last place is worth $130,000.
Players who qualified based on their official world rankings included Phil Mickelson (2), Retief Goosen (4), David Toms (5), Love (7), Singh (8), Harrington (9), Furyk (10), Price (11), New Zealand's Michael Campbell (13), Chris DiMarco (14) and Estes (15).
Bernhard Langer, Rich Beem, Montgomerie and Skins Game winner Mark O'Meara received special exemptions.