French Open: Kerber and Azarenka exits leave women's draw wide open as Serena wins in under 45 minutes

Kerber defeat to world No 58 and Azarenka's injury withdrawal leave way clear for champion Serena

Angelique Kerber became the second Australian Open champion to fall at the first hurdle in Paris in three years (Getty)

The women’s tournament here at the French Open was regarded from the start as one of the most open contests for many years.

The first-round defeats of Angelique Kerber and Victoria Azarenka, who were viewed as two of the more likely title contenders, throws the door open even wider than ever.

Kerber was beaten 6-2, 3-6, 6-3 by the world No 58, Kiki Bertens, of the Netherlands, while Azarenka retired hurt with a knee injury when losing 6-3, 6-7, 4-0 to Italy’s Karin Knapp, the world No 118.

The results can only be good news for the defending champion, Serena Williams, who began her campaign with a 6-2, 6-0 victory over Magdalena Rybarikova. The world No 1 was on court for just 42 minutes.

Kerber, the world No 3, became the second Australian Open champion to lose in the first round here in the last three years, Li Na having suffered the same fate in 2014.

Kerber withdrew from last week’s Nuremberg tournament because of an injury to her left shoulder and it was clear that she was still not fully fit.

The 28-year-old German, who left the court for treatment when 3-0 down in the deciding set, did not hit the ball with her usual fluency.

She saved two match points when Bertens served at 5-3 in the deciding set, but on the third she put an attempted drop shot into the net.

“First rounds are always tough in the tournament, especially for me,” Kerber said afterwards. “What can I say? It happens.”

Although Kerber has performed well on clay in the past, her form had tailed off in recent weeks.

She lost to Barbora Strycova in the first round in Madrid and to Eugenie Bouchard in the second round in Rome.

While Kerber was forced to pull out of Nuremberg, Bertens won both the singles and doubles titles there.

Her singles triumph was only her second on the main tour and helped her to climb 31 places in the world rankings.

However, in 15 appearances at Grand Slam tournaments the Dutchwoman has progressed beyond the second round only once, when she reached the last 16 here two years ago.

Azarenka established herself as one of the favourites for Roland Garros when she won the titles in Indian Wells and Miami, but the former world No 1, whose career has been hampered by injuries in the last two years, has suffered more physical problems in recent weeks.

This time she suffered a knee injury, for which she first called for the trainer at 3-3 in the second set.

At 5-5 Azarenka seemed barely able to move and smashed her racket on the ground in frustration, but she gritted her teeth and forced a tie-break, which she won 8-6 after saving a match point.

In the final set, however, it was clear that she was struggling and after going 4-0 down she retired.

Victoria Azarenka retired through injury in the third set against Karin Knapp (Getty)

Kevin Anderson, Philipp Kohlschreiber, Federico Delbonis and Fabio Fognini were among the beaten seeds in the men’s tournament, but Novak Djokovic, the world No 1, and Rafael Nadal, who is chasing his 10th French Open title, both opened up with impressive victories.

Djokovic beat Taiwan's Yen-Hsun Lu 6-4, 6-1, 6-1, while Nadal crushed the big-serving Australian Sam Groth 6-1, 6-1, 6-1 in just over an hour. The Spaniard made only three unforced errors in the match.