Weeks before a leak of inside information led state investigators to question whether daily fantasy football games were a fraud, misleading thousands of players vying for millions of dollars in prize money, Madison Calvert, a regular player, became suspicious.

At a private party for DraftKings, one of the biggest daily fantasy websites, Calvert said, he discussed his baseball contest choices with a host, Jon Aguiar, an executive of the site, who suddenly made a quick check on his phone and, to Calvert’s surprise, informed him that his pick of a pitcher was a poor choice because many other players had selected him.

“I shouldn’t have pulled that up in front of you, ha-ha,” Calvert said Aguiar told him.

That was days after Calvert, 29, had repeatedly been challenged for head-to-head play in another game, on the website FanDuel, by a Rick Sawyer. After checking a search engine, Calvert said, he found that Sawyer was actually a business planning manager at DraftKings.

“I could only think that he had watched my DraftKings account and had me pegged as a suboptimal player,” Calvert said. “I felt like a moron.”