Horgan's inclusion comes on foot of an impressive first half showing against Ulster before he was forced out of the game just after the break with presumably the same stomach ailment that sidelined Keith Earls earlier in the day.
Speaking ahead of the game, Munster coach Declan Kidney said: "We want to win the Magners League so we have to be knocking on the door like Leinster have been doing in the last few seasons. You need to be up there, coming second or third before you can go on and win it, so I want us to be finishing as high up the league as we can.
"Winning is a habit and losing is a habit. We lost against Ulster on Wednesday so we've just got to try and win the next one.
"There's going be a lot of pride at stake on their side. I don't think it (Phil Davies' sacking) will affect the Scarlets. People could say we have distractions with a European final coming up in a few weeks' time, but the players are preparing for this game in a professional manner."
Post-script: Munster have been forced to make a late change to their matchday squad for Saturday's encounter with Llanelli.
Illness has forced Anthony Horgan to withdraw from the province's 22-man panel, with his place on the bench going to Brian Carney.
MUNSTER (v Llanelli Scarlets): Denis Hurley; Doug Howlett, Lifeimi Mafi, Rua Tipoki, Ian Dowling; Ronan O'Gara, Tomas O'Leary; Marcus Horan, Jerry Flannery, John Hayes, Donncha O'Callaghan, Paul O'Connell (capt), Alan Quinlan, David Wallace, Denis Leamy.
Replacements: Frankie Sheahan, Federico Pucciariello, Mick O'Driscoll, Donnacha Ryan, Peter Stringer, Paul Warwick, Brian Carney.