Newcomer Edna Anyango upset Women Fide Master (WFM) Sasha Mongeli on the first day of the National Chess Championships at Parklands Sports Club on Wednesday.
Anyango from Bank of Africa, won in 58 moves in a game that lasted more than three hours.
No one had given the unknown Anyango a chance of winning the match as she had been paired against a player, who was last week named the Star Times player of the Month after an outstanding performance during the Olympiad in Georgia.
A delighted Anyango said she had not expected to win but took advantage of her opponent's blunder.
"She left her queen exposed and I took advantage to capture. I am very delighted by the this win since I had expected at best a draw.
On her part, Mongeli said the blunder had made it impossible for her to recover but she expressed confidence of doing well.
In other matches, Cynthia Awino upset Olympian Daphne Mwikali.
Defending champions Ben Magana and Joyce Nyaruai won their opening matches. Magana edged out Andrew Owili while Nyaruai was too good for eight year old Janki Nipul Shah.
The win has bolstered the chances of Magana and Nyaruai to win their titles for the second year in a row.
Nyaruai needed just 34 moves to win her game.
"I made a mistake and she took advantage of it but it was a great game for me. I hope to do better in the coming games," she said.
National under-16 champion Timothy Mwabu easily swept aside Owen Ochieng as the national chess championships started at Parklands Sports Club.
It was Mwabu's first major tournament since he took part in the Africa Youth Chess Championships in Kisumu in August and he took less than half an hour to dispatch off his opponent.
Walela Austin 1-0 Kahihu Daudi, Stephen Kariuki 1-0 Theodore Warui, Chege Kariuki 1-0 Mark Warui, Kibe Neville 1-0 William Wachira, Hillary Sagwe 1-0 Mathenge Githuga, Ben Nguku 1-0 Fred Sagwe, Ernest Otanga 1-0 Martin Munene.