In a new promotion at Canterbury Park, the Shakopee track is offering 2-for-1 drink specials when the first gray horse to run on a given day wins its race. Richie Gary came through Friday, taking the first race of a 66-day season to bring a little extra cheer to a crowd announced at 6,237.

The gray gelding wasn’t facing very long odds. Richie Gary had to beat only three other horses in the smallest field of a numbers-challenged opening night. Canterbury often struggles to fill races early in the season when horses still are arriving, and with Oaklawn Park in Arkansas extending its season through this weekend, the calculus became even more complicated.

Most of the 300 to 400 horses coming to Shakopee from Oaklawn are still in Arkansas. Only 50 horses ran in Canterbury’s eight races Friday, and while it hoped to run nine races Saturday, it could only fill eight.

With so many tracks vying to attract quality horses — and a growing number racing on Kentucky Derby weekend — Canterbury officials will feel the squeeze while waiting for the barns to fill up.

“Derby day is a big day for on-track business, and it makes sense to run a live card if you can,” said Andrew Offerman, Canterbury’s director of racing. “Unfortunately, it gets tougher and tougher.

“There are six tracks running on Derby day this year that weren’t running last year. We’ve never seen a day like this before. That just makes it really, really hard to fill races.”

Offerman expects Canterbury’s stables eventually will house 1,500 horses this season, with 800 on the grounds now.

He praised Minnesota owners for having so many of their horses ready to race despite the slow-to-arrive spring, allowing Canterbury to run plenty of races for Minnesota-breds during the early days of the season.

Canterbury will race only 11 days in May while horses continue to arrive and get into racing shape. The jockey colony also will grow. Jareth Loveberry, Canterbury’s 2017 riding champion, is expected to be here next week, and at least three other riders will be coming soon.

About 14 to 16 trainers who plan to race in Shakopee this summer have yet to arrive as well.

The stable of 12-time training champ Mac Robertson won two races on opening night, though Robertson himself was at Churchill Downs. He will saddle Amy’s Challenge — Canterbury’s horse of the year in 2017 — for a $500,000 race on Saturday’s Kentucky Derby undercard.

Not long after Richie Gary’s victory, a persistent rain chased most of the spectators inside. Total handle on Friday’s live races was $673,232 with $128,915 bet on-track.

Saturday’s weather is expected to be ideal, and Canterbury expects a robust turnout of people — if not horses — for Derby day.

“I’m happy with the number of Minnesota-breds running,” Offerman said. “But you’d always like to see more horses in the entry box.”