2015: two-year-old season Gun Runner won two of three starts at age two.
2016: three-year-old season Gun Runner won four of nine starts at age three, also finishing second twice and third twice. Gun Runner began his three-year-old campaign on February 20, 2016, in the Grade II
Risen Star Stakes at the
Fair Grounds Race Course. With new jockey
Florent Geroux, he settled in fourth, then started his move around the final turn. He hit the lead at the head of the stretch, then held off a late run from Forevamo to win by half a
length. "He's a very nice horse. We're very lucky to have him," said trainer
Steve Asmussen. "I thought Florent gave him a beautiful trip with how the track was playing. He's shown talent the whole time and it's definitely good to see him in the winner's circle in a race like this." On March 26, Gun Runner returned in the $1 million
Louisiana Derby, also at the Fair Grounds, where he was the third betting choice at odds of just under 4–1. He was close behind a slow early pace, then drew away in the stretch to win by lengths. "The good thing is he's very easy to manage,” said Geroux. "He has so many gears. He settles really nicely, and when you ask him to go, he has a nice turn of foot." Gun Runner earned 151 points and ranked first on the
2016 Road to the Kentucky Derby, a series of races through which horses qualified for the
2016 Kentucky Derby. In the Derby, he was the third betting choice behind the two-year-old champion
Nyquist, who had also won the
Florida Derby, and
Exaggerator, who had won the
Santa Anita Derby. Gun Runner broke well and raced with Nyquist just behind a fast early pace set by Dazzling Candy. As they rounded into the stretch, Gun Runner took the lead. Nyquist then responded and started to draw away. From far behind, Exaggerator made a strong run down the stretch to finish second, with Gun Runner holding on for third. With his
connections opting to pass the final two legs of the Triple Crown, Gun Runner returned to action on June 18 in the
Matt Winn Stakes at
Churchill Downs. He led from wire to wire, winning by lengths while setting a stakes record. His time of 1:41.12 for miles was 0.02 seconds off the track record. His next start saw him face Nyquist and Exaggerator again in the 2016
Haskell Invitational Stakes. On a sloppy track, he ran an uncharacteristically off-the-board race, finishing fifth. He rebounded with a third-place finish in the
Travers Stakes, though well behind the winner,
Arrogate, who set a track record for 10 furlongs with a final time of 1:59.36. "We ran into a freak today," Asmussen said. "I thought 2:02 would win it." On September 24, Gun Runner again faced off with Nyquist and Exaggerator in the $1.25 million
Pennsylvania Derby at
Parx Racing. He settled into fourth behind a fast early pace, then swung wide around the far turn to move into second. Meanwhile, Connect made his move along the rail and reached the lead in mid-stretch, then stood off Gun Runner's rally to win by half a length. After finishing second in the
Breeders' Cup Dirt Mile, Gun Runner ended his three-year-old season on November 25 against a strong field of older horses in the
Clark Handicap at Churchill Downs. When expected pacemaker Noble Bird broke poorly, Gun Runner took control of the race and led from wire to wire for the first Grade I win of his career. "I'm so proud of him," said Asmussen. "Walking him over, the horse has such confidence about him. He's kept his strength and his weight with the thousands of miles he's traveled this year on the stages that he's been on."
2017: four-year-old season Gun Runner won five of six races at age four. His only loss was a second-place finish behind Arrogate in the Dubai World Cup. He turned the tables on Arrogate in the 2017 Breeders' Cup Classic, which helped him earn Horse of the Year honors. Instead, Gun Runner's 2017 seasonal debut came in the Grade III
Razorback Handicap on February 20 at
Oaklawn Park. Sent off as the 1–5 favorite in a field of six older horses, Gun Runner took the lead out of the gate and was never seriously challenged to win as he went miles in 1:40.97, two-fifths of a second off the stakes record of 1:40. The win cemented Gun Runner's reputation for durability, reliability, and "consistent class" and encouraged his connections to run him in the $10 million
Dubai World Cup. "He's getting better and better and (the Razorback) was an extremely pleasant performance, even better than anticipated,” said Doug Cauthen of Three Chimneys Farm. "He's a heck of a nice horse and he's proven it." On March 25, Gun Runner entered the Dubai World Cup at
Meydan Racecourse in
Dubai as part of a field of fourteen that was headlined by Arrogate, who had won the
Breeders' Cup Classic and
Pegasus World Cup after defeating Gun Runner in the Travers. On a muddy track, Gun Runner tracked the early leaders, then took the lead as the field turned for home. He continued to stride out well but succumbed to Arrogate, who overcame a terrible start to win. Gun Runner's second-place finish earned him $2 million. After the Dubai World Cup, his connections announced that Gun Runner would run against Arrogate at least once more, in the 2017 Breeders' Cup Classic.
Summer On May 1, it was announced that Gun Runner's next start would be in the Grade 1
Stephen Foster Handicap at Churchill Downs on June 17. The Stephen Foster is a "Win and You're In" race, part of the
Breeders' Cup Challenge series. The winner of each "Win and You're In" race gets an automatic berth into a specific Breeders' Cup race, which for the Stephen Foster is the Breeders' Cup Classic. Highweighted at 124 pounds, Gun Runner drew post 3 in the Stephen Foster and was installed as the 4–5 morning line favorite. By post time, his odds had dropped to 1–2. Sent out to the lead early, Gun Runner set the pace and led the field into the first turn and onto the backstretch. On the second turn, 10–1 shot Stanford attempted to make a bid for the lead, but Gun Runner drew away to win by 7 lengths, a record margin of victory for the Stephen Foster. His final time of 1:47.56 was 0.28 seconds off of
Victory Gallop's track record set in the 1999 Stephen Foster. He was given a Timeform US rating of 139 for his performance, tied with Arrogate in the Pegasus World Cup for the highest Timeform rating achieved within the US in 2017 until that point. Asmussen was relieved that Gun Runner had earned his spot in the Breeders' Cup Classic early. "There's not more I can say than this horse is simply the real deal,” he said following Gun Runner's Stephen Foster win. Jockey Florent Geroux was also very impressed with Gun Runner's performance. "You know, going back and thinking about the race, it's very rare as a jockey that you can feel a horse never getting tired in a 1 1/8-mile Grade 1,” he remarked. Gun Runner made his next start in the
Whitney Stakes on August 5 at Saratoga, going off as the heavy 3–5 favorite. After a good start, he settled into second place behind Cautious Giant, who had been entered as a "rabbit" for his stablemate War Story. Entering the far turn, Geroux decided the pace was too slow and let Gun Runner assume control of the race. In the stretch, he continued to draw away to a length victory, despite a strong late run from
Keen Ice. The win attracted further attention on social media because Gun Runner ran the final half mile with a horseshoe caught in his tail; a shoe from Cautious Giant flew loose just as Gun Runner was starting his move. "We watched the tape repeatedly, repeatedly,” said Asmussen, "and if you never seen anything before, just wait around. Can you believe that? I mean, if we tried to throw one and stick in one's tail as he was standing, still we'd go 0-for-1,000 – let alone at a run, let alone Gun Runner, let alone in the Whitney – and it stayed. [With] how fast he was going [during the race], it was held out from him. When he slowed down to walk, then it came into him. We were obviously unaware of it until he came back to the winner's circle, but not a nick on him. I mean, there's still nails in it." The shoe was originally thrown out by Asmussen's assistant trainer Scott Blasi, but after realizing the rarity of the situation Blasi paid $100 to a fan to get it back. It was eventually given to Asmussen's children. The race improved Gun Runner's rating to 127 in the Longines
World's Best Racehorse Rankings August update, third place worldwide.
Autumn On September 2, Gun Runner made his next start in the
Woodward Stakes at Saratoga, going off as the prohibitive favorite in a field of five. Trainer Todd Pletcher entered two horses, with Neolithic assigned to set a fast early pace in the hopes of tiring Gun Runner, while Rally Cry was intended to close from behind. The race went much as expected, with Gun Runner stalking Neolithic for the first 6 furlongs before swinging to the lead on the far turn. Gun Runner maintained his momentum and won by lengths over the late-closing Rally Cry. His time of 1:47.43 was the fastest Woodward Stakes since the race was moved to Saratoga in 2006 He was also given a Timeform US rating of 142, the highest rating that the organization had ever assigned. "That was better than the Whitney, just stronger, faster overall,” said Geroux. "I don't think he's 100-percent cranked up yet. I really do think we have another step forward with him. We're going to need one against Arrogate." A few weeks after the Woodward, Asmussen sent Gun Runner to California with Blasi, exercise rider Angel Garcia, and groom Gabino Gutierrez, allowing the horse time to acclimatize. The
2017 Breeders' Cup Classic was help on November 4 at
Del Mar Racetrack. Going into the race, handicappers were divided over who was the best horse in North America. Arrogate's victory in the Dubai World Cup over Gun Runner had been ranked as the best performance of the year up to that point in the World's Best Racehorse rankings, but Arrogate had suffered two losses after returning to the United States. By contrast, Gun Runner had won three straight Grade I races and appeared to be getting stronger. Gun Runner was made the 9–5 morning-line favorite over Arrogate at 2–1 in a field of eleven. By post time, the odds on Gun Runner had drifted out slightly to 2.4–1, making him the second betting choice.
Collected, who had beaten Arrogate in the Pacific Classic earlier in the year, was the third choice. Gun Runner broke well and quickly moved up to the lead with Collected pressing him on the outside. They ran the opening quarter in a rapid 22.50 seconds, then Gun Runner opened a slight lead as he moved around the first turn and down the backstretch. Geroux kept him on a light
rein, later saying that the horse was relaxed and happy, "flopping his ear back and forth." Rounding the final turn, Collected closed ground and the two were head-and-head with a quarter of a mile remaining. Entering the stretch, Gun Runner responded to the challenge and again pulled away, winning by lengths. Arrogate was never a factor in the race after breaking poorly, finishing in a dead heat for fifth. Gun Runner earned a career-high Beyer Speed Figure of 117
2018: Pegasus World Cup On January 25, 2018, Gun Runner was voted
American Champion Older Dirt Male Horse and
Horse of the Year for 2017. He became the third Horse of the Year winner for trainer Steve Asmussen. Two nights later, Gun Runner entered his last race, the
Pegasus World Cup. He drew an outside post position, which was cause for concern in a race of miles at
Gulfstream Park, where the start is very close to the first turn. However, Geroux used Gun Runner's early speed to get racing room and moved quickly towards the rail, settling in second place just to the outside of Collected. The two set a brisk early pace, then Gun Runner made his move on the far turn. Collected dropped back but West Coast started to close, getting to within a length in mid-stretch before Gun Runner responded by pulling away to a length win. Gun Runner ended his career on a five-race winning streak – all of them Grade 1 tests. The $7,000,000 winner's purse brought his lifetime earnings to $15,988,500, which ranks second all-time among North American-based thoroughbreds. ==Racing statistics==