FORT WORTH — After months of delays, the trial of Eric Kay opened on Tuesday as federal prosecutors began to make their case that the former communications director of the Los Angeles Angels had supplied drugs to a pitcher, Tyler Skaggs, that led to the player’s death by overdose in 2019.

Skaggs’s death shook baseball deeply, serving as a reminder of the breadth of a national opioid epidemic. And it led to a widespread investigation that eventually centered on Kay. But on Tuesday, as Kay began his defense, his lawyer tried to turn that narrative on its head, suggesting that Skaggs had, in fact, been Kay’s drug supplier and not the other way around. And he said that the drugs that led to Skaggs’s death may have come from his teammate, pitcher Matt Harvey.

Kay was indicted on charges of conspiracy to possess with intent to distribute a controlled substance, and conspiracy to possess with intent to distribute a controlled substance resulting in death and serious bodily injury. He pleaded not guilty.

After Tuesday’s jury selection, which lasted around three hours, Lindsey Beran, an assistant U.S. attorney, opened the case by telling jurors that Skaggs, a popular pitcher who overdosed in a suburban Dallas hotel room two weeks shy of his 28th birthday, was dead because Kay, who had served as his drug dealer, provided him with drugs that contained ethanol, oxycodone and fentanyl.

Beran said Kay supplied Skaggs with a blue pill or pills, disguised to look like oxycodone, that was in fact fentanyl, a different opioid that is cheaper to produce and far more lethal.

“It was the fentanyl in his system that actually killed him,” Beran said.

Kay’s lawyer, Reagan Wynn, argued that the relationship between Skaggs and Kay had been misconstrued. He said his client, who was addicted to oxycodone, had been supplied with pills by Skaggs and a clubhouse attendant, Hector Vazquez, for multiple years before Skaggs’s death.

Wynn said that Kay tried to seek treatment for his drug addiction — court documents support that Kay sought treatment in April 2019 — but that he had fallen back into using when Skaggs asked him to obtain drugs for the road trip to Texas.

According to Wynn, Kay arranged for the purchase of oxycodone. Later, Wynn said Kay witnessed Skaggs using other drugs, which his client claims Skaggs identified as Percocet — a combination of oxycodone and acetaminophen. According to Kay’s version of events, Skaggs told him that he had obtained the Percocet from Harvey.

Harvey is on the list of potential witnesses in the trial.

The trial, which will resume Wednesday, and likely will continue into next week, could see dozens of witnesses take the stand, including several former teammates of Skaggs.

The first witness to testify was Andrew Heaney, a pitcher for the Angels and Yankees in 2021 who had previously been a teammate of Skaggs. Heaney testified that he did not know Skaggs was abusing opioids.

Marina Trahan Martinez reported from Fort Worth and Benjamin Hoffman from Connecticut.