LOUISVILLE, Ky. — Bob Baffert had so much success in his early years at the Kentucky Derby he thought it would go on forever. Three wins in six years will do that. Then karma caught up and sent him into a humbling slide.

He’s hoping to change his luck Saturday, when he saddles Pioneerof the Nile, the early co-second choice in the morning line. The colt is Baffert’s first serious contender since he won his third Derby in 2002.

‘‘He has the fight in him,’’ he said.

For the first time in a while, so does Baffert.

‘‘I’ve been obsessed with the Derby, but how can you not be? Any trainer that doesn’t want to win the Derby needs to take another job,’’ he said.

Baffert nearly won America’s most famous horse race in his first try in 1996. Cavonnier lost by a nose to Grindstone and trainer D. Wayne Lukas, igniting a rivalry between the veteran and the brash newcomer.

‘‘There was a time we just couldn’t stand each other,’’ Baffert said. ‘‘He raised the bar and I was trying to get to it.’’

It didn’t take long. Baffert won the following year with Silver Charm and repeated in 1998 with Real Quiet.

‘‘I’ve spoiled myself,’’ he said. ‘‘It was getting to the point where I thought, ’Oh, this is easy.’’’

Then the Derby gods intervened.

Baffert kept finding a way to show up on the first Saturday in May, failing each time to get anywhere near the winner’s circle.

‘‘I’ve been in the paddock and saddled horses and just felt nothing,’’ he said. ‘‘I told my wife Jill, ’I’m not going to bring a horse up here if I feel like I don’t have a chance.’ It’s just not fun for me.’’

Baffert hit rock bottom in 2001 after Point Given, sent off as the 9-5 favorite, was second turning for home and wound up fifth. His other horse, Congaree, led with a quarter-mile to go only to get beaten by four lengths. In 2002, he picked up War Emblem three weeks before the Derby and the colt scored a gate-to-wire victory, finally returning Baffert to a familiar spot and the joy of hoisting that gold cup.