That means Nick De Luca drops to the bench and Jim Thompson misses out altogether while Alasdair Dickinson has recovered from an abdominal upset and replaces Geoff Cross on the bench in the other change.
Danielli's inclusion sees Max Evans switch from his place on the wing to a starting berth at outside centre alongside powerhouse Graeme Morrison.
Andy Robinson's men bid for history as the first Scotland team to win a cap Test series overseas after their 24-16 win in Tucuman and the former England boss has warned his players to wipe the slate clean.
"The scoreboard starts at 0-0 and the Pumas await," Robinson said.
"I've brought in Simon Danielli and moved Max Evans to his normal centre spot which he plays for Glasgow having looked at the way we want to attack Argentina in the outside channels.
"Simon runs hard, is pretty direct and I've been impressed by his form for Ulster in the Magners League, where he has been a regular try scorer.
"Selection was a tough call for a number of players and, as management, we've expressed our admiration for the commitment of the entire squad to securing a win on Saturday."
Scotland: Hugo Southwell, Sean Lamont, Max Evans, Graeme Morrison, Simon Danielli, Dan Parks, Rory Lawson, Allan Jacobsen, Ross Ford, Moray Low, Jim Hamilton Alastair Kellock, Kelly Brown, Johnnie Beattie, John Barclay.
Replacements: Scott Lawson, Alasdair Dickinson, Scott MacLeod, Alasdair Strokosch, Mike Blair, Phil Godman, Nick De Luca.