Riley addressed Wade's departure during a news conference Saturday, one day after the 12-time All-Star officially signed a two-year deal with his hometown Bulls.
"What happened with Dwyane floored me," Riley said. "I'm going to miss the fact of what I might have had planned for him and his future and how I saw the end and my thought process in how I could see his end here with the Heat. ... It's my responsibility to sort of make that happen. I didn't make it happen. Dwyane left, and the buck stops here."
Wade said last week that a "business" rift with Riley played a significant role in his decision to end his 13-year career with Miami. Wade helped lead the Heat to three NBA championships and is the franchise's all-time leading scorer.
Riley, the Heat's president, admitted that he was not as involved in the negotiation process as he needed to be in order to retain Wade, who turned down Miami's two-year, $40 million offer earlier this month in favor of Chicago's two-year, $47 million offer.
Riley wasn't in New York when the Heat last met with Wade on July 6, only a few hours before he announced that he was picking Chicago. In that last meeting, which was handled by Heat managing general partner Micky Arison and CEO Nick Arison, the team's offer was raised slightly -- though not to the level of what Chicago was able to pay.
"I have great regret I didn't put myself in the middle of it and immerse myself in the middle of it and get in a canoe and paddle to the Mediterranean if I had to, be in New York when he arrived on the 6th and greet him at the airport," Riley said. "I wasn't there in the middle of the negotiation, and that's my job. It's not going to be the same without him. We will forge ahead."
Riley said he believes Wade's decision wasn't fueled by money, but rather something else.
"That is where we both failed ... I more than he, because he's the asset, he's the star, he's the face of the franchise,'' Riley said. "I should have done everything that I could have verbally in trying to change his mindset to mine, a big picture, a better picture, or one that I thought would help him."
Whether that would have worked is unknown, and irrelevant now anyway. Wade went home to Chicago, and for the Heat it's time for the aftermath that follows whenever there's a superstar-level goodbye. Riley has been through it plenty of times before in Miami, whether it was Alonzo Mourning or LeBron James or Shaquille O'Neal or Brian Grant or Eddie Jones.
This, Riley said, is different.
"We've had a tough summer," he said.
Riley said he hasn't spoken with Wade since he decided to leave the Heat. Riley has been working on an email to send Wade at some point, and he expects that when they see each other again, a warm embrace will be involved.
"My thoughts were always to try to make the team better and at the same time try to make sure that Dwyane, over the course of the three, four, five years that he had left in his career, that he was going to get his money," Riley said. "He would get it -- but not at the expense of paralyzing our ability to win. If there's anything I could have done better, I would have done it. But right now, there's no do-overs in this thing."
Information from The Associated Press was used in this report.