As he watched the simulcast of Saturday’s Kentucky Derby, David Hooper could tell something was amiss as the leaders came out of the final turn.

“I thought I saw something happen that was different than normal,” said Hooper, the presiding steward for the Minnesota Racing Commission. “The horse with the white silks suddenly dropped back very quickly, and I knew something caused it.”

Hooper left Canterbury Park immediately after the race, not learning until later that the winner, Maximum Security, had been disqualified. By Monday, he had seen video and photos that led him to the same decision as his Kentucky peers. Hooper said Maximum Security clearly interfered with other horses when he drifted out on the turn, and the job of the stewards — whether at the Kentucky Derby or Canterbury Park — is to enforce the rules.

The three Churchill Downs stewards who disqualified Maximum Security and declared Country House the winner have not answered any questions about how they came to their decision. Hooper said they likely had “the weight of the world on their shoulders” when they considered the central issue Saturday: Was the incident severe enough to affect the outcome of the race?

“That’s the ultimate responsibility of any steward who works the Derby,” said Hooper, who started as a steward in the mid-1970s and is in his seventh season at Canterbury. “It isn’t just any other race. It is the Derby. But there are rules.

“It’s unfortunate. You hate to take the best horse down, and it appeared Maximum Security was probably the best horse in the race. But from everything I’ve seen and read, I have no doubt they made the right call.”

Hooper, a 59-year veteran of the horse racing industry, has made those calls as a steward at tracks from Kentucky to Texas to Minnesota. During the Canterbury Park season that started last Friday, he and two colleagues — David Smith and Stan Bowker — will follow the same protocols used around the country, including at Churchill Downs.

Jockeys or trainers can lodge an objection if they believe a foul was committed. The stewards, who observe the races from a booth high in the grandstand, also can initiate an inquiry if they see something of concern. They will look at video from five cameras placed at different points around the track, and they also interview the jockeys.

Hooper said stewards will not take down a winner without solid reasoning, and most decisions at Canterbury are unanimous. It doesn’t happen often; in 667 races at Canterbury last summer, there were 48 inquiries or objections, and 12 horses were disqualified.

In the Derby, Hooper said, War of Will challenged for the lead even after Maximum Security drifted out and impeded him. That met the standard of whether the interference was serious enough to affect the outcome.

“The question arises, what if the incident hadn’t occurred?” Hooper said. “War of Will was right up there. [Jockey Tyler] Gaffalione was looking for room. What if Maximum Security hadn’t come out like that, and Gaffalione finally had an opening, and he ended up rushing on through and taking the lead?

“But War of Will had to deal with the incident. So that’s why I believe the right call was made.”

Tom DiPasquale, executive director of the Minnesota Racing Commission, said there has been discussion of changing North American disqualification rules. In many other countries, a horse is disqualified only if the horse it impeded clearly would have beaten it.

Both sets of rules have the same objective: Keeping the horses and riders safe. Given that Maximum Security could have knocked War of Will off his feet, Hooper was grateful that the debate centered on the stewards’ decision and not something more serious.

“The riding in the Derby has gotten so rough, we could have had a major accident,” he said. “Thank God we aren’t talking about a disaster today.”