An extension could still be reached before Saturday's deadline, Rondo's agent, Bill Duffy, told ESPN The Magazine's Ric Bucher on Tuesday.
Celtics director of basketball operations Danny Ainge and Duffy met at Tuesday night's Celtics-Cavaliers game in Cleveland, and the team made a counterproposal that has rekindled negotiations.
Duffy told Yahoo! Sports on Monday that talks of an extension were dead after a message from the team indicated the Celtics' offer would not change. Rondo was prepared to test the market next summer as a restricted free agent.
But the two sides kept their scheduled face-to-face meeting in Cleveland, anyway. Terms of the counterproposal were not available, but it was enough to re-open dialogue, Duffy said.
According to multiple reports earlier Tuesday, the Celtics and Rondo's representatives met recently to try to work out a deal but were far apart.
"We're not going to do an extension right now," Duffy had told Yahoo! Sports. "The conversation has been cordial. We've been talking the last couple of weeks. There is a difference between the perception of him in their eyes and our eyes. With that being said, the focus is on Rajon to have a fantastic season and concentrate on winning a championship."
Before the Celtics' opener against the Cavaliers in Cleveland on Tuesday, Rondo wouldn't comment on his contract status.
"It'll take care of itself," he said. "I'm focused on Cleveland right now."
Duffy said he is looking for a deal that would make Rondo one of the NBA's top five highest-paid point guards. According to Duffy, the Celtics "feel differently," Yahoo! Sports reported.
An unnamed source told Boston sports radio station WEEI that the Celtics offered Rondo a five-year, $45 million extension (an average of $9 million per year), but Rondo is seeking a five-year deal worth between $55 million and $60 million (an average of $11 million to $12 million per year).
Should Rondo become a restricted free agent, he could receive contract offers from other teams after the season. The Celtics would have the right to match any offer he received.
Rondo is making $2.3 million this season in the last year of his rookie contract. He averaged 11.9 points, 8.2 assists and 5.2 rebounds per game last season.
ESPNBoston.com's Chris Forsberg contributed to this report. Ric Bucher covers the NBA for ESPN The Magazine.