Viswanathan Anand went down to Armenian Levon Aronian in the first round of the Zurich Chess Challenge.
It turned out to be a bad day in office for Anand, who lost his way in the middle game and his counter play bid did not materialise.
World champion Magnus Carlsen outplayed Boris Gelfand of Israel in a remarkable game.
The other game of the six-player round-robin tournament between Fabiano Caruana of Italy and Hikaru Nakamura of United States ended in a draw.
With four rounds in the classical chess remaining and then five in the rapid stage to be played, Carlsen and Aronian emerged as the early leaders on two points each and they are followed by Nakamura and Caruana with a point apiece.
Gelfand and Anand will look forward to open their account in the second round.
The tournament has a unique format wherein the classical and rapid scores will be clubbed together to find the winner.
Every classical win gives two points, draw one and a loss none while in rapid every win gives one and a draw a half point.