Queensland captain Munster has played all 15 club games he was available for this year as well as three State of Origin matches for the Maroons, including the 30-12 loss to NSW in the Origin decider on Wednesday night in Brisbane.
Storm coach Craig Bellamy has given the five-eighth a rest for Sunday evening's clash at AAMI Park, given Melbourne have a five-day turnaround before playing Sydney Roosters next Friday night.
Munster indicated after the Maroons loss that he wouldn't be playing this match.
"I've probably got to think about the body as well. I haven't had a break and it's been 18 games straight," he said.
Maroons hooker Harry Grant and bench forward Trent Loiero got through the Storm's captain's run on Saturday and both are set to back up.
Utility Tyran Wishart is expected to line up at No.6 for the Storm in Munster's absence but Melbourne also have Trent Toelau in their 19-man squad who can play in the position.
Keeley, who secured a mid-season release from the Dolphins after agreeing to join the Storm from next season, is a boost to Melbourne considering their injuries in the pack.
"We signed him for next year but we were fortunate the Dolphins were willing to let him go for the rest of this year," Bellamy said.
"He's only been here a week but he has made a really good impression. I am pretty sure he will add something to the squad."
The Storm are still a slim chance of playing finals.
The similarities in the seasons of last year's grand finals combatants is stark.
The Storm lost seven games in a row earlier in the season and sit in 11th position, four points outside the top eight.
The 2025 premiership-winning Broncos have lost a shocking eight matches in a row and are 14th.
The difference is the Storm have had a mid-season renaissance and are far better placed to make the finals.
However, Storm legend Cameron Smith said on Channel Nine this week his former club can't afford to lose any of their remaining matches.
Munster had a slightly different take on the task ahead.
"We've got a bit more of an easier run (than the Broncos), but we've still got to do it tough," Munster said.
"We can afford to probably lose one or two more games and then that's it.
"It would have been nice to beat Manly into the bye last week because it would have given us a chance of being in the eight or even the four.
"We're still breathing down their necks. If we can put some games together, who knows?"
The Storm will notch their 500th win in the NRL since entering the competition in 1998 if they topple the Titans.
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