Kentucky Derby favourite American Pharoah, ridden by exercise rider Jorge Alvarez, gallops at Churchill Downs in Louisville, yesterday.

BOB affert is riding high these days, knowing he holds a pair of aces heading into the Kentucky Derby. The white-haired trainer has the probable favourite in either undefeated Dortmund or American Pharoah, giving him a double shot at winning America's greatest race for the fourth time.

He's just not his old cocky self about it.

At 62, having survived a heart attack three years ago in Dubai, Baffert feels grateful to be back in position to win another Derby, which would move him into a tie for second-most among trainers. He hasn't smelled the roses since 2002 with War Emblem.

"This is the time of year where we take nothing for granted, we work hard, we have a great team," he said, spreading the credit around to his stable help. "We want to get there in top form and healthy. That's the battle right there."

Todd Pletcher is even luckier. He's got five horses set to run tomorrow in the one-mile race, with Blue Grass winner Carpe Diem as his leading contender.

Pletcher's mentor, D. Wayne Lukas, has a shot at making Derby history. The 79-year-old Hall of Famer could become the oldest trainer to win with Mr Z.

The four-time Derby winner would surpass Art Sherman, who was 77 when California Chrome won last year.

Dortmund comes into the Derby with a 6-0 record, equaling the marks of Seattle Slew and Smarty Jones when they won the Derby in 1977 and 2004, respectively.

He's got the pedigree, too, having been sired by 2008 Derby winner Big Brown. His front-running style could keep him out of trouble in the jammed field.

American Pharoah romped to an eight-length victory in his last race at the Arkansas Derby.

His sire, Pioneer of the Nile, finished second in the 2009 Derby.