Free agent David Martin has been training with Charlton this week, News Shopper understands.
Martin, 31, has been without a club since leaving MK Dons in May.
Addicks boss Karl Robinson brought the goalkeeper to the Dons in 2010, and he made over 300 appearances for the club.
Martin was training with Charlton earlier this summer, but did not feature in any pre-season games.
Robinson signed Bolton goalkeeper Ben Amos on a season-long loan last weekend, and made it clear that the former Manchester United man would be his number one this season.
News Shopper has been told that Martin, who has played at Championship level, wants regular first-team football.
MORE: Robinson on why Arsenal youngster's proposed move to Charlton broke down
And that is something Robinson would not be able to guarantee.
However, if Martin does join the Addicks, it will allow highly-rated Charlton stopper Dillon Phillips to go out on loan.
Phillips, 22, enjoyed a successful loan spell with Cheltenham, winning promotion to League Two in the 2015/16 campaign.
But on his return to SE7 last season, he played second fiddle to Norwich loanee Declan Rudd.
Robinson is keen to bring in another goalkeeper before the transfer window shuts to ensure Phillips gains first-team experience.
His potential replacement, Martin, was at the Valley to watch Charlton's 6-1 win over Ipswich last weekend.
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