A partnership of nearly 20 years will reach its zenith on Saturday when Creative Cause runs in the Kentucky Derby for trainer Mike Harrington and owner Heinz Steinmann, both of whom will have their first Derby starter. “He’s been the greatest man in the world to me,” said Harrington, 71, who first met Steinmann, 80, a ski-resort developer, in the early 1990s. “He gave me $700,000 to go buy a Derby starter. I came home with three horses. How many owners give you a blank check and say, ‘Good luck?’ ” Of the three horses Harrington purchased for Steinmann, one was Creative Cause, who has been a mainstay on the West Coast since his debut last summer. He won the Norfolk Stakes last fall, finished third in the Breeders’ Cup Juvenile, and this year won the San Felipe before a narrow loss in the Santa Anita Derby. Creative Cause, and the other two well-bred runners Harrington acquired for Steinmann, were purchased with the idea of hoping at least one could replace Swiss Yodeler, who, at age 18, is nearing the end of his successful stallion career. Swiss Yodeler was the first top-class horse for Harrington and Steinmann. His major wins included the Hollywood Futurity and Hollywood Juvenile Championship in 1996. “He’s been a very successful stallion in California. A cash cow,” Harrington said. “Mr. Steinmann was trying to get a horse to replace him. “This horse,” Harrington said, referring to Creative Cause, “is positioned to do well as a stallion. These stud horses are kind of a legacy for him.”