Rennie has a question mark over Charlie Ngatai, who suffered a concussion in last weekend's loss to the Hurricanes, but the Chiefs are hopeful their starting centre will pass subsequent protocols after ticking off the first set.
The injury crisis that plagued the locking stocks has cleared and in Sam Cane and Hika Elliot, two integral parts of the side's backbone will return rested and ready for the winner-take-all encounter.
All things considered, having watched his side fall against the Hurricanes and forced on the road, Rennie was rosy ahead of the trip to Dunedin. But his mood was nothing compared to that of Hammington.
Having made a positive impression on Rennie in 2011, when he and Kerr-Barlow were world champion Baby Blacks halfbacks, the Manawatu man has this year had a hectic season.
Hammington has spent the season shuttling between Palmerston North and Hamilton, offering injury cover to the Chiefs while enjoying regular runs for Feilding. He was more than happy to trade club rugby for a knockout battle.
"It's being thrown in the deep end a little bit but it's pretty exciting and I'll be happy with anything," he said. "Just training with the boys for this long has been awesome and, if I get a run, it'll be a dream come true."
Weber will naturally take the No9 jersey from kickoff and, if all goes to plan, Hammington may not even be seen in a Chiefs jersey. After all, a tight tussle could see Weber play 80 minutes, while Kerr-Barlow is pushing hard for an unlikely return should the Chiefs advance.
But, having started the season in fifth spot on the depth chart, merely having the chance to experience this environment is reward enough.
"I'm right down the list. Leon [Fukofuka, wider training group halfback] has been injured for quite a lot of the season, I suppose, so I've been up here for quite a while, just in the background."
If Hammington moves to the forefront on Saturday night, it will also be owed in part to the opponent he will be attempting to edge. Having soaked up Aaron Smith's advice during the pair's Manawatu days, the similarly-statured Hammington has modelled his game on the All Black.
And together with Weber and Fumiaki Tanaka, the undersized quartet will have a big impact on which side stays alive.
"We certainly won't be four of the biggest halfbacks," Hammington laughed.