The experienced hooker successfully came through a rigorous session this morning (Tuesday) at Thomond Park, and will add to coach Tony McGahan's options as Munster look to get back to winning ways.
Last Friday's Division 1A game against Garryowen was Flannery's first run-out since he sustained the injury in action for Ireland against the Barbarians last June.
"My last game was the Barbarians match, so that was the bones of four months ago. I was delighted to get onto the field and very grateful to Shannon for giving me the opportunity to get some rugby," he told the Limerick Leader.
"What it came down to was that a nerve was getting pinched in my back. That was why I kept tearing my calf. We didn't figure this out for a while.
"The feeling was this is a calf injury, it shouldn't be dragging on this long. So that is why I got the anti-inflamatory injections in the spine. It was to help soothe the nerve and fix things. It has worked so far.
"I am almost ahead of schedule hitting this game against Garryowen. Originally, I wasn't aiming to be back until this week.
"Everything has gone well so far. There is a lot of rugby to play. The trick now is to try and stay fit. There is a lot of competition everywhere for places. If you are not fit, you are not even considered.
"Hopefully, I will be considered for selection. They may want me to play some more club rugby or they may want me involved in the game with Toulon. That is up to the management team."
The selected Munster squad includes all 23 players who were on duty for the pool opener against London Irish last Saturday.
Among them is centre Sam Tuitupou who will appear before an ERC disciplinary hearing in Dublin on Wedenesday, after being cited for an alleged dangerous tackle.
Flanker Alan Quinlan is in line to win his 202nd provincial cap this weekend, ousting his former team-mate Anthony Foley as Munster's most-capped player.
Danny Barnes, Darragh Hurley, Billy Holland and Peter O'Mahony also feature in the extended panel.
MUNSTER Squad ( v Toulon) - Backs (11): Duncan Williams, Peter Stringer, Ronan O'Gara, Scott Deasy, Paul Warwick, Danny Barnes, Keith Earls, Johne Murphy, Sam Tuitupou, Doug Howlett, Denis Hurley.
Forwards (18): Wian du Preez, Marcus Horan, Mike Sherry, Jerry Flannery, Damien Varley, John Hayes, Darragh Hurley, Tony Buckley, Billy Holland, Donnacha Ryan, Donncha O'Callaghan, Mick O'Driscoll, Alan Quinlan, David Wallace, Niall Ronan, Denis Leamy, Peter O'Mahony, James Coughlan.