The 29-year-old winger made more than 250 appearances for the Lions before joining Sheffield United in 2005 and is now back training in south London after leaving Selhurst Park.
"Paul is a free transfer from Crystal Palace and he's looking for somewhere to train and do his pre-season," said Jackett.
"I'd be lying if we weren't looking at each other as a prospective club and as a prospective signing, so we'll see how he goes, how he fits in and how his fitness is.
"He has other offers on the table, as you would expect, but it will be interesting to see how he does this week."
Jackett is likely to make a decision on Ifill by the end of the week before the squad leave for a pre-season tour of Ireland.