The 28-year-old midfielder has been told he is surplus to requirements and can leave in the January transfer window or at the end of the season when his contract expires.
Though a first-team regular only weeks ago, Tabb has dropped down the pecking order following the recent signings of midfielders Daniel Carrico and Hope Akpan.
The ex-Coventry City and Brentford star admitted: "I had an honest chat with the gaffer, he pulled me in and said I'm probably not needed any more and if something comes up in January I can go or wait until the end of the season on a free. It was a totally friendly conversation, we shook hands.
"I've played 12 or 13 games this season and done pretty well. Obviously the club signed two more midfielders and without a new contract offer it was kind of expected, the writing was on the wall.
"It's one of those things and I said to him I'm here until the end of the season if needed he can rely on me."
Tabb has made 105 Royals appearance since joining from Coventry City in January 2009.
He added: "It happens in football, you can't stay forever. Of course I wanted to stay but you can't force clubs to keep you.
"Like I say, it's one of those things and I'm sure if I move in January the club will wish me well and I will wish the club well.
"The fans have been great to me, the same with the players. If I'm needed before the end of the season they can rely on me."
++ NOEL HUNT is set to open talks with Reading over a new contract.
The 29-year-old's current deal is set to run out in the summer and he is keen to extend his four-and-a-half year stay at Madejski Stadium following a £600,000 transfer from Dundee United.
Striker Jason Roberts is in a similar position to Hunt and is also seeking a new deal. But the 34-year-old has suffered from niggling injuries this season and is currently sidelined with a knock. ++