Having made just 15 runs in his last Shield clash against Tasmania, Kellaway found a new gear in hitting 66 off 142 balls to set up Victoria's chase at CitiPower Centre (Junction Oval) on Sunday.
His 102-run partnership with Peter Handscomb (48 runs of 78 balls) anchored Victoria's innings before both were taken in quick succession.
Kellaway edged off-spinner Nathan McSweeney behind, while in the following over Handscomb was also caught by Australian keeper Alex Carey, off quick bowler Jordan Buckingham.
The not out pairing of Will Sutherland (42 runs off 82 balls) and Oliver Peake (44 runs off 161 deliveries) then powered Victoria to finish 5-266, trailing by 39 runs at the end of day two.
Carey also produced the moment of the day when his outstretched diving arm found Handscomb's leg-side nick.
Five different bowlers took wickets for South Australia after they were all out for 305 earlier in the day.
Victorian off-spinner Todd Murphy finished with 4-67 after taking the final scalp of Nathan McAndrew (19 off 44 balls) in the opening overs.
South Australia's batting and bowling performance comes after the visitors confirmed their spot in the final against Victoria, beginning on March 26 at Junction Oval in Melbourne.
Queensland was an outside chance to take the second-placed team's spot, but the Bulls' batting crumbled for 178 runs against Tasmania.
With the South Australians also taking five wickets, it helped the Redbacks create an unassailable buffer over Queensland on the table, even if the Bulls beat Tasmania outright, due to the competition's bonus points structure.
The system awards bonus points to teams that score more than 200 runs and for every wicket a side takes during the first 100 overs of the first innings.
