Deron Williams is reportedly down to two free agency options: The Brooklyn Nets and Dallas Mavericks. And the Mavericks are worried the star point guard is slipping out of their grasp.

Ken Berger of CBS Sports reported Wednesday that "executives working the phones Tuesday have detected a real concern from the Mavs that Williams will opt to join the Nets in Brooklyn next season."

One of the reasons cited for Williams' continued interest in staying with the Nets is his close relationships with coach Avery Johnson and general manager Billy King. Johnson was reportedly one of eight or so people who attended a dinner Tuesday night to celebrate Williams' 28th birthday. King said he was also invited to the celebration and expressed confidence that Williams will return to the Nets.

Williams has officially decided not to opt into the final year of his contract, a move that he has long planned.

For more on Deron Williams' offeseason, check back to this SB Nation New York StoryStream. Meanwhile, for more on the Brooklyn Nets visit the SB Nation blog Nets Daily.