There was a ripple of heartfelt applause for Petra Kvitova on her victorious comeback and, shortly afterwards, the now worryingly familiar pain of early defeat for the world No1, Angelique Kerber, as the French Open began in sunshine, showers and mixed emotions.

Court Philippe Chatrier – poorly patronised, as ever, while the lunchtime champagne glasses tinkled nearby – rose in a minor key to acclaim Kvitova when the popular Czech posted an impressive 6-3, 6-2 win over the outclassed Californian, Julia Boserup. After what she has been through, even the many empty seats did not concern the happy Czech.

Returning from the horrors of a knife attack in her apartment last December, she kept her emotions in check when she stepped on to the tournament’s showpiece court but let the tears flow in victory as freely as the left-handed forehand that blew the world No86 hard-courter off the clay in less than an hour and a quarter.

Her team have “courage, belief, pride” printed on their T-shirts, and Kvitova explained courtside: “I needed that to come back here and play this tournament.”

Marion Bartoli, the 2013 Wimbledon champion whose own long struggle with injury forced her retirement, told her: “It was like just yesterday, blasting winners all over the place.”

Kvitova did not hold back on power on either wing, and moved with assurance on a surface that has not always been kind to her. She reached the semi-finals here in 2012 but is better suited to the grass of Wimbledon, where she has won twice. Nine aces flew from Kvitova’s rehabbed left arm and wrist past the dazzled American, although five double faults and 20 unforced errors in a short match prevented an even quicker conclusion.

Later, Kvitova spoke of her relief and satisfaction. “It was a nice and really heartwarming welcome,” she said. “My team was there. My family was there. Everyone who helped me through the difficult time. I’m happy with the game, of course, but it wasn’t really about the game today. I already won. This match is special to me. I won for the second time.”

She added: “After we had a little break when the rain came, I ‘caught’ the racquet [on a shot] and it was a bit weird but, after one point, everything was OK. I was happy that I didn’t have any pain. I promised my doctor, who gave me the green light, that, if I feel pain in my hand during the match or in the practice, I’m stopping immediately. So I’m glad that I didn’t [have to].”

If handling the substantial trauma of a night-time assault in her own home was Kvitova’s greatest victory, Kerber has the comparatively mundane but nevertheless draining challenge of rediscovering the tennis and the self‑belief that elevated her to the top of her game over the past 18 months. It does not seem to be forthcoming.

Kerber is in more trouble than Michael Fallon, unable to correct a ship that has been listing alarmingly of late, and the normally resilient German could not avoid becoming the first world No1 to lose here in the first round in the Open era, when the unseeded, nothing-to-lose Russian Ekaterina Makarova beat her 6-2, 6-2.

Serena Williams lost in the first round to the then world No111 Virginie Razzano in 2012, when she was ranked fifth, and, in the American’s absence this summer from the tour and the top of the rankings while awaiting the arrival of her first child, Kerber had a chance to build on the late-arriving success of her breakthrough year in 2016, but appears to be blowing one opportunity after another.

She tried down to the wire in the hour and 22 minutes it lasted, but never really looked in the fight. Kerber lost more than half of her first serves, double-faulting four times, and Makarova worked her over on second serve as well. As desperation set in, Kerber went for the lines and paid the price with 25 unforced errors. There is little calm in her game and it might take a while to get it back.

As open as the women’s game has become, it is odd to see a fine player who won two slams and reached the final of another in the space of nine months lose to an opponent 40 places below her in the rankings.

Kerber also lost in the first round here last year, to 58th ranked Kiki Bertens, one of her 13 first-round exits in majors. Her clay season has been fairly miserable, as she lost first up in Stuttgart to France’s Kristina Mladenovic, retired in the third round against Eugenie Bouchard in Madrid and was helpless to stop the world No68 Anett Kontaveit in her first match in Rome. While that was her heaviest defeat by ranking in 18 months, Sunday’s loss was probably harder to take.

Kerber was near to inconsolable afterwards. “Maybe it’s good that it’s over for me,” she said. “I think I will go back home. I will do maybe a few days’ rest – or a few more days [practice]. I really don’t know what I will do now. But for sure I will think about what is the best preparation for grass.”

Kvitova and Makarova, meanwhile, could meet in the fourth round. However, in the febrile atmosphere of change that is sweeping through Roland Garros, that is far from a certainty for either player.

This video has been removed. This could be because it launched early, our rights have expired, there was a legal issue, or for another reason. Kvitova makes emotional return while top seed Kerber crashes out – video