Sifford died Tuesday at age 92. Sifford challenged the PGA Tour's Caucasian-only clause in 1961 and eventually won his way onto the tour. He won the Greater Hartford Open in 1967, the Los Angeles Open in 1969 and the 1975 Senior Championship.
"He's like the Grandpa I never had," Woods said after a Wednesday morning practice round in advance of the Farmers Insurance Open at Torrey Pines. "It's been a long night, and I'm sure it will be a long few days. He fought, and what he did, the courage for him to stick with it and be out here and play."
Woods said that without Sifford, "I probably wouldn't be here. My dad would have never have picked up the game. Who knows if the clause would still exist or not? But he broke it down."
Sifford helped pave the way for Woods, who has won 79 PGA Tour events and 14 major championships.
In 2004, Sifford became the first African American to be inducted into the World Golf Hall of Fame.
"I first met him when I started this job," PGA Commissioner Tim Finchem remarked in a Wednesday morning interview with reporters. "He was playing the Champions Tour in those days. It's a real loss, because he was a pioneer, he suffered all kinds of difficulty playing as an African American, and it's just a sad day."
Finchem said the PGA Tour will explore ways to honor Sifford's legacy sometime this season.
Many tour players competing at Torrey Pines this week were born years, even decades, after Sifford broke the discrimination barrier.
Brooks Koepka, the 24-year-old winner of last week's Waste Management Phoenix Open, said he was saddened by the news of Sifford's death.
"And my thoughts were with his family and everything," Koepka said. "But as far as a historian of the game, we're always studying, we're always looking at guys that have been here before us and learning from them."