Casince her comeback from a gender investigation, running third in the 800m in the ster Semenya fell to her first defeat Diamond League on Friday.
In her Diamond League debut - at the last meet on the schedule - the South African teenager finished in a time of 1minute 59.65secs, behind Kenyan Janeth Jepkosgei and second-placed Mariya Savinova.
Ninth-placed Jemma Simpson said while she felt it was 'fair' to see Semenya return from her 11-month absence, doubt would remain on her legitimacy while the results of the inquiry were remained unreleased by the International Association of Athletics Federations.
"One of the issues with some of is that no-one really knows what the outcome (of the gender inquiry) is," said Simpson.
"She's just been allowed to come back on the scene and we're expected to just get on with it."
"It's fair to an extent but I think but we just want a fair playing field out there. I know it's really none of our business but it would be nice to be reassured more than anything."
American Tyson Gay took out the 100m final in predictable fashion, but did not achieve his aim of breaking his personal best time.
He won in time of 9.79secs - 0.01secs behind his fastest time in 2010 he ran at Crystal Palace, which doubles as the American record.
Gay overcame a quick start from rival Nesta Carter to reel in his countryman, who finished second in 9.85secs.
World No.1 Bershawn Jackson took out the 400m hurdles over Welshman Dai Greene, who produced his season-best performance.
Greene's time of 48.26secs has given him hope he can break the 48-second barrier.
"I'm very pleased with the result," he said.
"I think that reinforces the result I had in Barcelona and shows I can go under 48 seconds."
Priscilla Lopes-Schliep was the first Canadian to win a Diamond League title, taking out the 100m hurdles.
She finished in a time of 12.54secs in the event at Brussels, ahead of second-placed Australian Sally Pearson.
Allyson Felix is the only winner of multiple Diamond League titles, saluting in the women's 200m and 400m.
Kenya's David Rudisha took out the men's 800m, two seconds off his world-record time he set in Berlin on Sunday.
Countryman Asbel Kiprop outlasted Leonel Manzano of the United States in the battle for the men's 1500m.
Croatia's Blanka Vlasic leaped highest in the women's high jump event, notching a height of two metres.