PARIS: Russia's Svetlana Kuznetsova, the 2009 champion and seeded 26 this year, marked her 40th Grand Slam appearance with a comfortable 6-1, 6-3 win over Croatian world number 117 Mirjana Lucic.
The 26-year-old Russian, who was also runner-up in 2006, brushed aside the 30-year-old Florida-based Lucic in just 61 minutes.
Kuznetsova tackles either Kateryna Bondarenko of Ukraine or Taiwan qualifier Chan Yung-Jan for a place in the last 32.
Despite Baltacha's defeat to Stosur, British hopes were boosted when Laura Robson, who had lost in qualifying, was handed a spot in the main draw as a 'lucky loser' after Spains's Silvia Soler-Espinosa pulled out with an injury.
Former Wimbledon junior champion Robson will face Anabel Medina Garrigues.
Robson joined fellow qualifier Heather Watson, Baltacha and Anne Keothavong in the main draw, making it the most British women in the first round in Paris for 21 years.
Later Sunday, Venus Williams and Juan Martin Del Potro, whose careers have seen Grand Slam highs as well as injury-hit lows, will take centre-stage.
With top drawcards such as Novak Djokovic, Rafael Nadal, Roger Federer, Maria Sharapova and Serena Williams all being spared opening day duty at Roland Garros, the likes of Williams and Del Potro get an early chance to impress.
Williams, now ranked 53 in the world after battling energy-sapping Sjogren's Syndrome, was runner-up in Paris in 2002, losing the final to sister Serena.
The 31-year-old begins her 15th Roland Garros against Argentina's Paula Ormaechea.
Del Potro, the only man to have won a Grand Slam title outside of the 'big three' in the last seven years, begins against Spanish veteran Albert Montanes.
Ninth-seed Del Potro was a semi-finalist in 2009 before going on to win the US Open that year.
But a wrist injury saw him sidelined for nine months before his ranking slumped to 485.
Del Potro won the claycourt title in Estoril this year and could face Federer in the quarter-finals at the French Open.
Two other former champions are also in action on Sunday.
Juan Carlos Ferrero, the 2003 men's winner, faces France's Jonathan Dasnieres de Veigy while Ana Ivanovic, the 2008 women's champion, plays Lara Arruabarrena-Vecino of Spain. (AFP)