Jason Euell feels he has to leave Charlton this month to try to rescue his career.
The attacking midfielder, 28, was the Addicks' record signing when he arrived from Wimbledon in a £4.75million deal during the summer of 2001.
Despite proving an instant hit with 13 goals in his first season, the Jamaica international found his first-team opportunities last year after falling out of favour.
Then in August, he suffered a shoulder injury which kept him out of contention for the start of the new campaign.
Now fit again, Euell was on target for the reserves in Monday night's 3-0 win over Chelsea and maintains he needs to be playing first-team football sooner or later.
Both Birmingham - whom Charlton host on Saturday - and Portsmouth are said to be monitoring the situation, and with manager Alan Curbishley reported to be keen on a deal to bring Lee Bowyer back to his former club from Newcastle, Euell could be allowed to move on.
'I told Curbs that I feel I need a move and a fresh start at another club to get my career going again,' Euell said.
'The last 18 months has been a waste for me and I don't want that to happen this season.
'I know things can change around, but I've been fit for weeks now and not even got on the bench.'
Euell told the South London Press: 'I just need to be playing football, whether that comes from a loan move to another Premiership club or a permanent move.'
The midfielder still has another year and half left on his current deal, and believes he can still have an impact in the top flight.
Euell added: 'I don't want to go to a Championship club - I feel have proved myself at this level.
'All this has gone on too long for me now and it's time for a clean break.
'If I'm not in the manager's plans, I can't wait around on the off-chance I'll get the odd game here and there. I have to think about my career.'
Charlton head into Saturday's clash with Birmingham at The Valley buoyed by their FA Cup win at Hillsborough, a welcome relief from the inconsistent form in the Barclays Premiership.
The Addicks will host east-London neighbours Leyton Orient in the fourth round, and have allocated the Coca-Cola League Two club some 6,000 tickets.
Chief executive Peter Varney explained: 'Under FA rules, we are obliged to give visiting teams in the FA Cup 15% of the seats in the stadium, which in our case would be just over 4,000.
'However, Orient demonstrated in the last round that they can attract a sizeable following, and with this being another derby match they felt they would comfortably sell 6,000 tickets.
'It is always our primary aim to prevent having away supporters in home areas. Obviously by giving Orient 2,000 tickets more than the competition rules stipulate, we are doing all we can to avoid this situation.'
Varney added on the club's website, www.cafc.co.uk: 'Obviously it is regrettable that we have to move a number of our supporters and I apologise to those who are inconvenienced.
'However, hopefully they will appreciate we are doing this to make segregation easier.
'It still leaves more than 20,000 tickets for Charlton supporters and if we run out of those, it will be quite a nice problem to deal with.'