The Italian has come off contract at Sampdoria and is now training and playing with the PFA's free agent squad.
Ex-Premier League players Ravel Morrison, Paul Dummett and Tom Davies are also part of the ever-expanding group.
Borini's former AC Milan teammate Asmir Begovic also worked with the PFA squad before landing a contract with Leicester City.
He recalled: “I think the off season is always a challenging time in certain ways. You take your rest and recover from the long season before and then start preparing for the next season. Now without always knowing the date as to when you go back and when you need to be ready for, it’s quite difficult.
“What the PFA provide, especially with the set-up they have, that makes it real easy for players to dip in and dip out and get top quality coaching. So for me it was nice to be able to tick over, spend some time with the family, play some other sports and keep busy.”