Former New York Knicks star forward Anthony Mason's condition has only improved "slightly" since he suffered a massive heart attack earlier this week.

According to The New York Times, the 48-year-old Mason went to a local hospital for a checkup for heart issues on Thursday and suffered a heart attack while there. Reportedly, family members have already been advised Mason will need a heart transplant if he survives.

"Right now, it's day to day, but that's an improvement from moment to moment," said Don Cronson, Mason's one-time NBA agent.

ESPN previously reported a source close to Mason confided with reporters he is "literally fighting for his life."

In all, Mason played 13 NBA seasons, five of them with the Knicks under coach Pat Riley. Playing both forward spots, the 6-foot-7, 260-pound Mason thrived in Riley's tough-minded, defensively focused system. Starring alongside Patrick Ewing, John Starks and Charles Oakley, Mason was named NBA Sixth Man of the Year during the 1994-95 season when he averaged 10 points, eight rebounds and three assists on 57 percent shooting from the field.

Mason played under Riley again in 2000 when both were with the Miami Heat. Over his career, he averaged 10.9 points and 8.3 rebounds. His best overall statistical season came with Charlotte in 1996-97 when he averaged 16.2 points, 11.4 rebounds and 5.7 assists.

Before joining the Denver Nuggets for his first NBA season in 1989-90, Mason played several seasons abroad in Turkey and Venezuela. The Knicks moved to sign him before the start of the 1991-92 season. He was traded to the Charlotte Hornets in 1996 in a deal that landed the team forward Larry Johnson.

"Our thoughts and prayers are with Anthony Mason and his family," Knicks officials posted on the team's Twitter account.