Adrian Wojnarowski explains how the Celtics and Cavaliers finalized the Kyrie Irving-Isaiah Thomas trade with Boston by adding a 2020 second-round pick to seal the deal. (1:51)

With a Thursday morning deadline looming, the Boston Celtics agreed to send the Cleveland Cavaliers a 2020 second-round draft pick via the Miami Heat to acquire four-time All-Star guard Kyrie Irving and complete the blockbuster trade.

The Celtics resisted the Cavaliers' desire for a first-round pick to compensate the Cavs' reluctance to sign off on Isaiah Thomas' hip injury, and Cleveland finally agreed to consummate the deal late Wednesday night.

Irving is scheduled to be introduced at a news conference in Boston on Friday, league sources said.

These talks had become a game of chicken, with both teams risking the consequences of walking away on a deal that could have short- and long-term consequences for each franchise.

Last week, the Cavaliers and Celtics agreed on a deal that was intended to send Irving to Boston for Thomas, a two-time All-Star, forward Jae Crowder, Ante Zizic and an unprotected 2018 first-round draft pick via the Brooklyn Nets.

Cleveland maintained that Boston wasn't fully transparent about the possible length of rehabilitation facing Thomas, who suffered the hip injury in March and was shut down in the Eastern Conference finals. Thomas has been rehabilitating his injury, and he told ESPN on Tuesday that he expected to play this season and believed he would return to an elite level. The Celtics believe they were fully forthcoming in detailing Thomas' injury, sources said.

"There's never been an indication that I wouldn't be back, and there's never been an indication that this is something messing up my career," Thomas told ESPN on Tuesday. "Maybe I am not going to be back as soon this season as everyone wants me to be, but I'm going to be back, and I'm going to be the same player again. No doctor has told me anything different than that."

Thomas, 28, is entering the final year of his contract and has been expected to be in line for a $100 million-plus contract in free agency. He had the best season of his career in 2016-17, averaging 28.9 points per game. In his three seasons with the Celtics, Thomas emerged as one of the NBA's elite guards.

The 2020 pick that Cleveland will receive from Miami was sent to Boston in the Zoran Dragic salary dump in July 2015.

Information from ESPN's Bobby Marks contributed to this report.