2014: two-year-old season

Firing Line began his racing career in a six-furlong maiden race at Santa Anita Park on October 25, 2014. Ridden by Mike Smith, he started favorite but despite finishing strongly he was beaten half a length by Alright Alright. Five weeks later he started 1/2 odds on favorite for a similar event at Del Mar and won by more than four lengths after taking the lead a furlong from the finish. On his final appearance of the year, Firing Line was moved up sharply in class to contest the Grade I Los Alamitos Futurity on December 20. After racing in second place he overtook Mr Z to gain the advantage in the straight but was caught in the final strides and beaten a head by the favored Dortmund.^[8]

2015: three-year-old season

On his three-year-old debut, Firing Line, ridden by Gary Stevens, contested the Grade III Robert B. Lewis Stakes at Santa Anita on February 7 in which he received five pounds from Dortmund. Firing Line overtook Dortmund on the final turn but was headed again by his rival in the closing stages and beaten a head. After the race, Stevens admitted that he may have made his move too soon.^[9] On March 22, Firing Line ran in the Grade III Sunland Derby against six opponents and started 1/5 favorite despite an unfavorable inside draw. He disputed the lead from the start and drew away in the closing stages to win by more than fourteen lengths from Where's The Moon. Callaghan said that the colt "really ran the race he hoped he would... you can't ask more than that" whilst Stevens praised the winner's attitude saying "he probably handled things a lot better than I did. He makes easy work of it and the best thing he's got going for him is his mind".^[10]

Firing Line before the running of the Preakness Stakes

On May 2, Firing Line contested the 141st running of the Kentucky Derby at Churchill Downs and started 9.5/1 fourth choice in the betting behind American Pharoah, Dortmund and the Blue Grass Stakes winner Carpe Diem. Ridden by Stevens, he tracked Dortmund before moving past his rival to take the lead on the final turn. He looked likely to win before being overtaken inside the final furlong by American Pharoah and finished second, a length behind the winner and two lengths ahead of Dortmund in third. After the race Callaghan said "I'm very proud of how well my horse ran. Gary rode a great race, he had him in the right spot. We just got beat. We tried all the way".^[11] Stevens attributed the loss to the colt's failure to change leads in the homestretch. Former jockey and racing commentator Richard Migliore theorized that the "wall of noise" from the Derby crowd unnerved the horse and distracted him from his rider's commands.^[12]

Two weeks later, Firing Line met American Pharoah and Dortmund again in the Preakness Stakes at Pimlico Race Course. He started the 3-1 second favorite to the Derby winner on a sloppy track after the course was hit by heavy rain and a thunderstorm. He stumbled exiting the starting gate and never contended, finishing seventh of the eight runners, more than forty lengths behind the winner, American Pharoah. Callaghan commented "he stumbled badly. That took his momentum, and he never really got hold of the track. Nothing went right with all that rain coming." Fellow rival Dortmund also had difficulties in the slop and finished fourth.^[13]