Jil Teichmann suffered a shock exit in the first round of the Transylvania Open as Anastasia Gasanova came from behind to win 4-6 6-0 7-5.
The competition's fourth seed and world number 39 started off well against Russian Gasanova, who is only ranked 146th by the WTA, but was crushed in the second set and was unable to recover in the decider.
It is a disappointing result for the Swiss, who made it to the final of the Western and Southern Open in Cincinnati in August, losing to world number one Ashleigh Barty.
Ana Bogdan won 7-6 6-4 on home turf against Ivana Jorovic and will likely play US Open champion Emma Raducanu in the round of 16 if the third seed can beat Polona Hercog on Tuesday.
Raducanu is still without a coach after parting with Andrew Richardson, and she faced the media on Monday, saying: "I am going to find my tennis, I just need a little bit of time.
"I don't think there is any pressure on me. I feel like everyone should just be a little patient with me."
Bogdan will also expect compatriot and top seed Simona Halep, with the two-time grand slam champion facing another Romanian in Elena Gabriela-Ruse on Wednesday, to join her in the next round.
What an epic battle!— Transylvania Open (@TransylvaniaOpn) October 25, 2021
It's the qualifier, Anastasia Gasanova, who prevails in what could be the match of the day. Saved two match points to defeat Jill Teichman, 4-6, 6-0. 7-5.
The key? "I said to myself, there is no chance to do mistakes". Worked wonders pic.twitter.com/QxWYNT9yvk
Meanwhile, fifth seed Clara Tauson enjoyed a comfortable 6-2 6-2 win over Stefanie Voegele in the Courmayeur Open in Italy.
Sixth seed Alison Riske and 10th seed Dayana Yastremska both won in straight sets to ensure there were no upsets in today's games, beating Ankita Raina and Vitalia Diatchenko respectively.