Serena Williams saw her hopes of an extended run at the Emilia-Romagna Open come to an early end on Tuesday, the top seed succumbing to Katerina Siniakova in straight sets. (More Sports News)
Williams had taken up a wildcard to play in the tournament following an early exit in Rome, where she was beaten by Nadia Podoroska in her opening contest in the clay-court swing.
Her campaign in Parma got off to a better start on Monday, a 6-3 6-2 result against WTA Tour debutant Lisa Pigato bringing a first triumph since losing in the semi-finals of the Australian Open in February.
However, the 23-time grand slam champion was unable to repel a determined Siniakova as she slipped out at the last-16 stage.
"It was a fantastic match and I played so well, I'm so happy that I could finish like that," Siniakova said after recording a 7-6 (7-4) 6-2 result.
"It was a pleasure to share the court with her.
"Now I will have the pressure because I defeated a great player, but I will enjoy it. I'm happy that I can continue and I will try to play my best in the next match."
Having failed to convert a set point opportunity, Williams hit back after losing serve with a break of her own to force a tie-break in the opener.
But Siniakova forced her way into a 5-3 lead before sealing it with a service winner, then quickly seized control of proceedings in a second set which was far less competitive.
Third seed Coco Gauff came through two tie-breaks to see off Kaia Kanepi, the American teenager having let slip a 5-1 lead in the second set before eventually sealing a 7-6 (8-6) 7-6 (9-7) win.
Petra Martic had no such issues in her opening contest against Varvara Gracheva, the second seed easing through 6-4 6-2 after one hour and 21 minutes on court.
Fourth seed Daria Kasatkina was eliminated, though, despite a dominant first set, going down 1-6 6-4 7-5 to Sloane Stephens.
At the Serbia Open, Kristina Mladenovic was the only seed to bow out, although she might have been grateful to avoid complete humiliation.
Anna Kalinskaya was made to work in the second but advanced in straight sets 6-0 7-6 (8-6).
Podoroska has made it a step further than she did after beating Williams in Rome, having reached the quarter-finals with victory over Oceane Dodin.
Paula Badosa is also through to the last eight, but Rebecca Peterson must still beat Ajla Tomljanovic to make the same stage.
