Chile won their friendly against Mexico with a last-minute winner on Tuesday night, whilst Sanchez played the full 90 minutes.
Sanchez, 29, had not played for his country since March, missing six matches - all friendlies - in the seven months away.
The forward had been called up in August but provided two different reasons for his absence - Chile's coach decided he needed more time to settle in at Manchester United.
Tuesday's match itself was decided with a goal from Nicolas Castillo, and Chile's next international fixture will be against Costa Rica in November.