Reigning champions Rajasthan were certain to retain the title after forcing a first innings lead of 326 runs, even as Dinesh Karthick 150 in 280 balls with 21 fours, one six, waged a lone battle for Tamil Nadu on the fourth day of the Ranji Trophy cricket championship final Chennai today. At close on the penultimate day, Rajasthan, despite enjoying a big first innings lead, did not enforce the follow on, and finished its second innings at 21 for no loss. Openers Aakash Chopra 10 and first innings hero Vineet Sharma 10 were at the wicket as their overall lead swelled to 347 runs. Tamil Nadu were all out for 295 in 102.4 overs after 464 minutes of batting, 16.4 overs after tea. At the M A Chidambaram stadium which had only a sprinkling of cricket lovers, Tamil Nadu resuming at the overnight score of 66 for three, kept losing wickets, with just the former skipper and stumper Dinesh keeping the innings afloat and went on to hit up his 11th Ranji 100.