A right-handed player, Schaerer was born in Asuncion and began playing tennis aged eight.

She was a member of the Paraguayan team that finished runner-up to Germany at the 1991 World Youth Cup, during which she was unbeaten in singles play.

While still a junior, she started her Fed Cup career for Paraguay, first appearing at the age of 16, including in a World Group tie against the Soviet Union.

[2] On the WTA Tour, her best performances came on the clay courts of the Copa Colsanitas in Bogotá, where she was a semifinalist in 1998 and quarterfinalist in 1999.

At the 1999 Wimbledon Championships, she and partner Alina Jidkova lost in the qualifying event but entered the draw as lucky losers.