While Sasikiran (4) rode high on his brains, the veteran Grandmaster Pravin Thipsay (2) was handed his second defeat of the tournament by Fide Master T S Ravi.

Thursday sole leader, Sasikiran, after beating Tejas Bakre in the fourth round, was one point ahead of his nearest rivals -- Abhijit Kunte (3) and R B Ramesh (3). Neelotpal Das (2.5) was third.

Playing the white side of the Najdorf defence, Sasikiran had double pawns on the c-file and an open b-file. He utilised the open file to pin down Bakre's pieces on the queen side. Then he focused on the King side. After brilliantly planting his knight on f5, he broke open the file to squeeze his rival further and gathered full points.

In the biggest upset of the fourth round, giant-killer T S Ravi ferociously attacked Thipsay's King, who blundered a piece onthe 26th move. Thipsay also overstepped the time limit, falling short of one move in the first time control.

The Kunte-Hegde game was replete with errors. Relying on his ability to defend, Hegde accepted Kunte's pawn offer early in the opening. The latter made no mistake in sacrificing another pawn to stall Hegde's progress. However, he missed a knock-out punch somewhere along the line in the sharp tactical battle and had to be content with the exchange and an extra pawn.Hegde had a chance to equalise when Kunte overlooked a simple check. But he wasted the opportunity by blundering a decisive move and allowed his rival to checkmate his king.

V Saravanan and DV Prasad agreed for a draw after a highly tactical game that was based on the Caro Kann defence. When they reached the ending with queen, two rooks and three pawns, they agreed for a draw. NK Mishra and Verghese Koshy shared points after 15 moves.

Anup Deshmukh's Boleslavsky variation of the Sicilian defence allowed P Konguvel to gain space on thequeen's side. Konguvel created a passer on the c-file and pushed it up to c-7, where it was captured by Deshmukh's rook on c-8. Konguvel lost control due to time pressure, to be held to a draw in 46 moves.

IM Neelotpal Das registered his first win outwitting Shankar Roy in a longer game of 63 moves.

Results (fourth round): K Sasikiran (4) bt Tejas Bakre (1), Abhijit Kunte (3) bt Ravi Hegde (1.5), R B Ramesh (3) drew with G B Prakash (2), Neelotpal Das (2.5) bt Shankar Roy (1), T S Ravi (2) bt Pravin Thipsay (2), V Sarvanan (2) drew with D V Prasad (1.5), Suvrajit Saha (2) drew with S K Rathore (2), P Konguvel (1.5) drew with Anup Deshmukh (2), N K Mishra (1.5) drew with V Koshy (1.5).

Fifth round pairings: A Deshmukh-N K Mishra, D V Prasad-P Konguvel, R G Hegde-Saravanan, G B Prakash-A Kunte, Shanker Roy-R B Ramesh, P Thipsay-Neelotpal Das, S K Rathore-T S Ravi, Tejas Bakre-Suvrajit Saha, V Koshy-Sasikiran.