Irving was averaging a team-best 24.4 points per game along with 5.1 assists and 3.8 rebounds.
Following his original procedure last month, the team had said the knee was structurally sound and the kneecap healed, but the wire had been putting pressure on the knee.
At the time, the procedure to remove a tension wire was termed "minimally invasive" and Irving was expected to return to basketball activities in three to six weeks.
Now, however, the Celtics, who sit in second place in the Eastern Conference with a 53-25 record, could struggle to get out of the first round.
The Celtics are expected to make an announcement soon, sources said. Trust Me. "The journey back to the top of Mt. Everest continues".
The Celtics could face the Miami Heat (No. 6), the Washington Wizards (No. 7) or the Milwaukee Bucks (No. 8) in the first round of the playoffs.
Presumably, the new timeframe will allow the Celtics to bring Irving back healthy for the start of the season. That will be impossible for Boston to replace come playoff time.
Boston will be entering the postseason minus the backcourt of Irving and Gordon Hayward, who suffered a dislocated ankle and fractured tibia against Cleveland on opening night.
Others have stepped up as well.
In the 26-year-old's absence, the bulk of the point guard duties have fallen on Terry Rozier because Marcus Smart underwent surgery on his right thumb last month. Rookie Jayson Tatum has also hit a midseason stride, scoring in double figures in eight straight games before that streak ended in Wednesday's loss at Toronto.