The Bon Jovi guitarist announced his departure from their Because We Can Tour last month citing ''personal issues'' and up until now the band have remained quiet as to his condition.
However, frontman Jon has now suggested it was an issue Richie has been through before - sparking speculation he is referencing Richie's last stint in rehab, for alcohol abuse, in 2011, which saw him miss out thirteen shows.
Jon said: ''It's getting more and more difficult every day to not just sit here and say something... Because all I can say is this - it's for personal reasons.
''He's been through it before, fortunately for us the same guy who filled in last time was available this time.''
Despite missing the musician, Jon, 51, is looking to the future and wants to make sure the band can still ''thrive'' under their strained circumstance.
He added to the Evening Standard newspaper: ''Life goes on, so if someone chooses not to be here... unlike if this were, God forbid, The Edge, and he for some reason couldn't make a U2 show, [then] it would be very difficult to just step in.
''You have a choice - you either figure it out, go and grow, not only survive but thrive. Or, you say, 'I hate my brother and I'm gonna quit the band.' ''
Phil X - who filled in during Richie's previous relapse - has stepped in as lead guitarist while Richie is away.