It was early evening on April 30, 1993, and about 6,000 spectators at the Rothenbaum Tennis Club in Hamburg, Germany, were watching the quarterfinal match between Monica Seles and Bulgaria’s Magdalena Maleeva. Seles had taken a 6-4, 4-3 lead before the changeover, and it seemed the world’s top player was on the verge of finishing off another routine victory.

Mid-changeover, a sudden scream jolted everyone’s attention to the court. Seles was lying on the ground, clutching her back. Security guards rushed to grab a pudgy, disheveled man who was standing near his victim and dragged him off the court, but the damage had been done. Gunther Parche, a 38-year-old unemployed lathe operator, had crept up to Seles, slipped a 9-inch boning knife out of a green bag and thrust it into her back, creating a half-inch-deep wound between her spine and left shoulder blade. The crowd watched, horrified, as the 19-year-old Seles was carried away on a stretcher and rushed to hospital.

News of the attack made headlines around the world. Because of Seles’ Yugoslav roots, it was initially assumed that the attack had been politically motivated. Instead, Parche had an entirely tennis-related goal—to restore Steffi Graf to the No. 1 position by forcing the German’s chief rival off the tour. Parche had obsessed about how to achieve his objective for months, and he saw his opportunity when Seles chose Hamburg as the site of her comeback from the viral illness that had sidelined her for three months.

There was worldwide shock at the violence, but the media underestimated the impact it would have on the star’s career. “Monica Seles is expected to be out of action for about four weeks,” was how early reports of the incident tended to end, also mentioning there was a chance she might miss Wimbledon.

This read of the situation factored in only the physical and not the psychological effects of the incident. Though Seles resumed practicing towards the end of 1993 and even thought about playing the 1994 Australian Open, she was increasingly troubled by memories of the trauma. The fact that Parche received only a two-year suspended sentence from the German courts worsened her state of mind.

Seles developed an “obsessive” fear of Parche and stopped sleeping at night. She could not stop reliving her memories of the stabbing, hard as she tried “not to see his face, hear my scream, smell the shirt and see the blood-caked knife.”

“My scream is what stayed with me a long time,” she said.

The once-bubbly teenager was also disillusioned by what she felt was unsympathetic treatment from the tour, including its decision to play the Hamburg event through to its conclusion. (Arantxa Sanchez-Vicario defeated Graf in the final.) “Nothing could change the reality that the tournament had gone on as if the attack had never happened. As if it didn't matter... I didn't matter,” Seles wrote in her 1996 autobiography.

With the exception of Gabriela Sabatini, the top players voted against freezing Seles’ WTA ranking during her time away. It was another slight. “Less than a week after Gunther Parche attempted to end my tennis career and quite possibly my life, the Women's Tennis association voted on the state of my ranking,” Seles wrote. “I had been the top female tennis player in the world, but there was no consideration given to my position.”

Seles felt in particular that Graf – given her indirect connection to what had happened – should have reached out more. Though she visited Seles at the hospital in Hamburg, the German was criticized for not mentioning Seles in her 1993 French Open victory speech, and the two had little contact during Seles’ two-year hiatus from the tour.

In the three years leading up to the stabbing, Seles had been the tour’s top performer, winning eight Grand Slams and losing just 15 matches. In her absence, Graf returned to dominance, winning six Slams between May 1993 and July 1995.

Appropriately enough, the two clashed in the final of the 1995 U.S. Open, the event which marked Seles’ return to the Grand Slam circuit. Graf was in commanding form, having lost just one match all year. Seles, who announced her comeback on the day Graf beat Sanchez-Vicario in the Wimbledon final, had since won all 11 of her matches in straight sets. Was she as good as ever?

The final turned on an inch. Holding set point in the first-set tiebreak, Seles hit what appeared to be an ace before the umpire overruled, and Graf ultimately went on to win the set (replays suggested the overrule was correct). Seles stormed back to take the second set 6-0, but faded in the third and lost 7-6(6), 0-6, 6-3.

The verdict was in: Seles was almost as good as her old self. And that, ultimately, wasn’t quite good enough Though she would win the 1996 Australian Open in Graf’s absence, the rest of Seles’ career was a slow but steady fade. There were fitness struggles; injuries; sadness surrounding the death of her coach and father, Karolj; and, increasingly, a younger generation sweeping her aside.

While not as successful on-court as she had been in her teens, Seles enjoyed far more public affection after her return to tennis. Before the stabbing, the giggly phenom with the machinelike, two-fisted groundstrokes (accompanied by notoriously earsplitting grunts) had sometimes been coolly received. The serious, almost saintly mature woman who returned in her place was a sympathetic figure always greeted warmly by the crowds.

For tennis, too, the episode represented an end of innocence. Security was increased and players became more wary of contact with the public. “Someone has broken through an invisible barrier,” Gerald Smith, then the executive director of the WTA, said after the attack. “Things are not the same today as they were yesterday.”

It is impossible to know what more Seles could have achieved in tennis had her career gone uninterrupted by a freak attack that day in 1993. But while debate goes on about how the sport’s history books were changed that day, there is no question that they were changed.

“The Return,” by S.L. Price in Sports Illustrated, July 17, 1995; “Savage Assault” by Sally Jenkins in Sports Illustrated, May 10, 1993; “Tennis star stabbed,” by BBC.com, April 30, 1993; and Monica: From Fear to Victory by Monica Seles and Nancy Ann Richardson were used as sources for this article.