Flanagan looks close to a move to Ibrox after completing a medical, according to 'Sky Sports', with the defender being a free-agent after being released from Liverpool.
The player burst on to the scene under Brendan Rogers, who is now manager of rivals Celtic, and made over 50 appearances for his boyhood club.
However, in recent years he suffered from issues with his knee and struggled to string a run of games together because of the injury problems.
Flanagan hit a low earlier this year, after he was given a 100 hour community order by a judge following the assault of his girlfriend.
Despite all of these issues on and off the field, Rangers assistant McAllister believes that the defender merits a second chance.
"It was unacceptable, most definitely. But he deserves a second chance. He showed remorse, he put his hand up and has taken his punishment. He wants to get on with his life and his football life," he argued
The deal for Flangan to be re-united with his former captain Steven Gerrard looks close, but will undoubtedly cause controversy because of the player's personal history.