CLEVELAND -- The Cleveland Cavaliers' biggest impending free agent might not even wear a uniform.

Cavs general manager David Griffin has been operating this season on the final year of his contract after failing to come to an agreement on an extension with ownership this past offseason, multiple sources told ESPN.

Griffin has presided over the team signing LeBron James, trading for Kevin Love and making two straight NBA Finals appearances -- the second resulting in the first championship for the city of Cleveland in 52 years -- since he was elevated from the Cavs' acting general manager following the dismissal of Chris Grant, to head GM in May 2014.

While doling out contract extensions to much of the Cavs' core in the last two summers -- James, Love, Tristan Thompson, J.R. Smith, Iman Shumpert and Richard Jefferson all inked multiyear deals totaling more than $395 million -- there has been no deal struck for Griffin himself. Cavs coach Tyronn Lue was also rewarded with a five-year, $35 million extension in July.

Some key voices inside the Cavaliers' locker room have spoken out in support of the GM, who has spent more than half his life working in the NBA after starting with the Phoenix Suns as an intern in 1993.

"It makes no sense why he shouldn't get an extension," James recently told ESPN. "He's pulled every move -- he's tried to make every move happen -- to better this team to be able to compete for a championship. So we wouldn't be in this position, obviously, without him and without the guys that are here -- from the coaching staff to the players to Griff. He's been a big piece of it."

James went on to rattle off the moves that Griffin implemented midseason during each of the past three years to give the Cavs a facelift.

"He went out, we needed some interior help, he went out and got Timo [Timofey Mozgov]," James told ESPN of the deal Griffin struck in January 2015. "We needed some perimeter defense, some perimeter shooting, he made a trade to be able to get Swish [J.R. Smith] and Shump [Shumpert]. And that was the start of it. We needed more interior depth, he got Perk [Kendrick Perkins]. We got guys. We brought guys in. We needed some more athletic wings, he made a move, I don't know how he finagled it to get RJ [Jefferson] here. And so on and so on ...

"I mean, all the guys that are here. We wanted a stretch-4 to help Kev out, we make a trade to get Channing [Frye]. I mean, I can name all the pieces that he's been able to [acquire]."

Lue, who shares agent Mark Carmony of CSE with Griffin, also recently spoke out about what the Cavs GM did this season to improve Cleveland on the fly.

"Griff's done a hell of a job," Lue said. "To acquire D-Will 2 [Derrick Williams], D-Will 1 [Deron Williams], [Kyle] Korver and [Andrew] Bogut without having any money, that's an amazing job. Griff's done a tremendous job. Every time someone goes down. Even last year, the year before when Timo and J.R. and those guys came in, he just always seems to work his magic when we need it and he's done a great job. Now it's my job to make sure I put everybody in the best possible way to be successful."

Griffin declined comment, and Carmony did not return several attempts by ESPN to contact him.

While having the benefit of the highest payroll in the league (north of $128 million) and the type of talent that wants to play for the Cavs, Cleveland's salary structure has caused Griffin to have to be creative in the margins. In Griffin's contract year, the GM has figured out a way to dump the salaries of injured players Mo Williams and Chris "Birdman" Andersen, while revamping the bench.

James acknowledged that Griffin's contract status mirrors the disrespect the GM has received because of the perception that James ultimately runs the franchise.

"Obviously they always want to bring my name into it and say that obviously, it's easier because guys want to be here because I'm here," James told ESPN. "But at the end of the day, he still has to press the right buttons because I'm not in the war room, I'm not in the draft room with those [front office] guys. I don't know how much we may be over the luxury tax or if we have a trade exception here or how that's going to work there or how many days we got to do this. So, it wouldn't, seriously, I don't know why it would make any sense to bring in a new GM. That don't make no sense."

While the Cavs have dominated the league with Griffin calling the shots -- save for their recent slump -- the GM has seen some of his peers be rewarded with contract extensions while he waits. When Griffin and the Cavs won the championship in 2016, they went through GM Masai Ujiri's Toronto Raptors in the Eastern Conference finals and GM Bob Myers' Golden State Warriors in the Finals. Ujiri signed a multiyear extension with Toronto in September, and the Warriors promoted Myers to the president of basketball operations while also signing him to an extension this past offseason.

In 2014-15, Griffin finished second to Myers for NBA executive of the year, which is voted on by a panel of their peers. Last season, while making the moves necessary to propel Cleveland to the title, Griffin finished just seventh for the award.

James suggested that while his presence on the court undoubtedly helps the Cavs, it also makes Griffin's job more challenging.

"Listen, there are a lot of GMs that don't want to help me and help us," James told ESPN. "I've seen it. I've seen it. I've been to six straight Finals and there's GMs in the Eastern Conference that are like, 'S---, if we can get him out of the f---ing way, we can get an opportunity to maybe represent the Eastern Conference in the Finals. So, I get that.

"He still is doing what he needs to do to help this ballclub win [despite that]. And when I came here, when I decided to come back three years ago, I looked Griff dead in the eye and said, 'Listen, I'm here to compete for a championship and that's it.' And he said, 'That's exactly what I want to do too.'"