His first season of racing at Canterbury Park didn’t go as well as Robertino Diodoro hoped. Instead of becoming discouraged, the trainer came back to the Shakopee track this year — and brought more than twice as many horses.

Diodoro kept 20 thoroughbreds at Canterbury last summer but also spent time tending to his stables in California and Canada. Impressed by the lively crowds and growing purses at Canterbury, he returned with more than 50 horses this year, with plans to make Minnesota his home base. Friday, Diodoro’s optimism was rewarded in grand style when his colt Ella’s Kitten easily won the first race of ­Canterbury’s 69-day season.

Canterbury officials are enthusiastic about this season, too. They anticipate the track will continue the gains in field size, wagering and racing quality that began last summer, when purses increased significantly. A crowd of 5,853 turned out for Friday’s eight-race card and wagered $182,768; total handle was $563,724, with the per-race average of $70,465, nearly $20,000 higher than last year’s opening night.

“The purses are good, they treat the horsemen well and it’s fun for the owners,’’ said ­Diodoro, the leading trainer at Arizona’s Turf Paradise last winter. “There are a lot of places across the country where there are 50 people in the grandstand. The whole atmosphere here, it’s a big attraction.’’

In the third year of its purse-enhancement deal with the Shakopee Mdewakanton Sioux Community, Canterbury will pay $13 million in purses — twice as much as it offered in 2011. That drew more than 2,000 applications for its 1,600 stalls at a time when many tracks around the country are having difficulty attracting horses.

Canterbury’s stables will be full for the second consecutive season. Eric Halstrom, its vice president of racing operations, said the track has the luxury of being more selective as well, allocating its stable space to higher-quality trainers. A deeper pool of talented riders has joined the jockey colony, with Turf Paradise riding champion Jorge Carreno joining such regulars as Dean Butler and Scott Stevens.

“We haven’t hit our peak yet,’’ Halstrom said. “As you look around the country, tracks are struggling for horses. Some of them are canceling race days. I think we’re going to outperform the industry.

“We want to leave the meet saying the quality of our horses and riders is as good as we’ve ever had. There’s no reason to believe that won’t happen.’’

Diodoro is among six trainers to bring 50 or more horses to Canterbury this summer, as the track celebrates its 20th season since reopening in 1995. The purse-enhancement agreement, which is adding $75 million to the purse fund over 10 years, has helped Canterbury thrive.

During a 69-day season last summer, the track drew the highest attendance and total handle since its reopening. The amount bet on Canterbury’s races at other tracks soared by 47 percent, and Halstrom said the improving field size and quality should push that figure higher. Canterbury has contracted with Churchill Downs to market its simulcast signal this year, and more locations will show Canterbury’s races.

The track raised its minimum stakes purses from $50,000 to $60,000 this year, with most paying $75,000 or more. A handful of new trainers have moved into its barns, including St. Paul native ­Shannon Ritter. A former jockey at Canterbury during its early days, Ritter now trains for WinStar Farms, one of the nation’s leading owners.

Canterbury also will break ground Monday on a $2.5 million, 30,000-square-foot event center near the grandstand. Track President Randy Sampson said the facility will help draw more special events, part of a strategy to pursue new sources of revenue. “We’re trying to figure out ways to grow,’’ Sampson said. “But with the racing, things have never been better. Everyone is very optimistic.’’

Friday’s crowd saw a major upset in the season’s first feature race, as two-time Canterbury horse of the year Heliskier was defeated in the 10,000 Lakes Stakes. Heliskier, a 1-10 favorite, faded in the stretch after a tough battle with Bourbon County through much of the race. Bourbon County lost by a nose to 12-1 shot Speakfromyourheart, and Heliskier finished third.