Cusiter sustained a knee injury while in action for his club, Glasgow, last month
Scotland rugby captain Chris Cusiter is on his way home from the tour of Argentina, having failed to recover from a knee injury.
Cusiter sustained the injury while in action for his club Glasgow last month.
Scotland's head coach Andy Robinson had hoped the scrum-half would be fit to play at least a part of the two-match Test against Argentina.
Rory Lawson and co-captain Mike Blair both played a part in Saturday's win in Tucuman and offer Robinson cover.
The Scotland coach said of Cusiter: "He has worked hard and has enjoyed this experience here.
"He has been developing his leadership within the group and he has contributed very well.
"But now we know that he is not going to be fit for this weekend, it's right for him to go home."
Meanwhile Argentina have made three changes to their squad ahead of Saturday's second Test against in Mar del Plata.
Scotland won Saturday's first Test 26-14 in Tucuman.
Beagles Bordeaux winger Rafael Carballo, Tucuman RC second rower Santiago Guzman and Dax scrum-half Nicolas Vergallo join the squad.
London Irish scrum-half Alfredo Lalanne, Montpellier prop Juan Figallo and Universitario La Plata second rower Mariano Galarza drop out.