Cleveland Cavaliers head coach David Blatt reacts in the second quarter against the Chicago Bulls in game one of the second round of the NBA Playoffs in Cleveland, Ohio, in this file photo taken May 4, 2015. The Cavaliers have fired Blatt halfway through the season, according to news reports.?[Photo/Agencies]

LeBron James's Eastern Conference-leading Cleveland Cavaliers on Friday fired head coach David Blatt, four days after suffering their worst loss of the NBA season, and replaced him with assistant coach Tyronn Lue.

The surprise move to fire the second-year coach, who took Cleveland to the NBA Finals last year, came with the Cavaliers (30-11) holding a 3-1/2 game lead in the East.

"Every decision is made as an answer to the following question: Does it put us in the best position to deliver championships to Northeast Ohio?" General Manager David Griffin told a news conference on Friday.

"It's made because we have a lack of fit with our personnel and our vision of how to use that personnel."

"I'm measuring more than wins and losses ... are we working toward a championship, are we building a championship culture?"

In his first NBA coaching job, Blatt compiled an 83-40 record with the Cavs and reached last year's NBA Finals before falling to the Golden State Warriors.

However, he did not seem to be accepted with full respect by some of the team members, including James.

The Cavaliers are heavy favorites to represent the East again in the NBA Finals but there has been growing concerns over their performance against the top teams in the Western Conference.

Cleveland have lost only two of their last 11 games but one was to the San Antonio Spurs and the other was a crushing 132-98 home loss to defending champions Golden State.

Griffin said he did not discuss the decision with any of the players but over the past month began to feel a change was needed.

"Are we trying to achieve something as a unit or as a collection of individuals? We need to build a collective spirit," he said. "Halfway through this season we have not yet developed this identity."

The general manager said Lue was taking over as head coach without an interim tag.

"I am more than confident that he has the pulse of our team and that he can generate the buy-in required to start to refine the habits and the culture that we've yet to build."

Lue, a former NBA player and assistant coach with the Celtics and Clippers, had agreed to a multi-year deal, according to media reports.

Prior to joining the Cavaliers, Blatt had no NBA experience but was a well-respected and accomplished international coach.

Blatt led the Russian national team to the 2007 Eurobasket championship, 2011 Eurobasket bronze medal and 2012 London Olympics bronze medal, and also led Israeli club Maccabi Tel-Aviv to six Israeli Cup championships and five league titles.

Blatt thanked the Cavaliers for the opportunity.

"I am proud of what we have accomplished since I have been the head coach and wish the Cavaliers nothing but the best this season and beyond," he said in a statement.