The defender is out injured himself and says he is targeting a return to action in December.
The young defender had started the season strongly since joining the Reds from Charlton Athletic over the summer, featuring heavily at left-back under former manager Brendan Rodgers.
He is now set to spend a significant period on the sidelines though, having suffered an anterior cruciate ligament injury to his right knee while on international duty with England's U21s last week.
And Flanagan says he will be there to offer his advice, should it be required, as he is recovering from a similar ailment himself.
"I'm devastated for him, I know what it's like to be in his situation with a long-term injury," Flanagan told Liverpoolfc.com.
"I spoke to him yesterday and just told him to stay positive and if he ever needs any advice to come and see me, don't hesitate. I know it's going to be tough for him but he's got to stay positive."
On his own rehabilitation, Flanagan says it will be a while before the Anfield faithful see him in the Liverpool team again.
The defender was a big part of Brendan Rodgers' side as they took the Premier League by storm in 2013/14, a season that saw them finish second in the table after coming agonisingly close to winning the title.
He last featured in the final game of that campaign, a 2-1 win over Newcastle United at Anfield, but missed the entirety of last season through injury, and says he is targeting December as a possible return date this term.
"I'm back running now and hopefully I can push on and get back in the team in a couple of months,” Flanagan added.
"I've just got to progress and get myself fit, building up my leg strength. [December] is the aim - if all goes well that's the plan. You've got to stay positive. It's mentally tough but I'm mentally strong."