Each one of the Chennai batsman, who took guard today, went on to score a half-century to put the hosts in a commanding position.
Chennai openers -- Abhinav Mukund (51) and KB Arun Karthik (50) -- laid the strong foundation by putting on 106 runs after the hosts elected to bat at MA Chidambaram stadium.
Ganesh Satish broke the stand when he trapped Karthik in the 35th over and Sunil Raju took the second and final wicket of the day exactly after five overs when he had Mukund caught behind.
Satish bowled only two overs in the day and did not bowl after dismissing Karthik.
Aparajith, who had excelled in India's under-19 World Cup triumph, and his senior partner Badrinath batted patiently for about 50 overs till the stumps were drawn.
Playing only his sixth first class game, Aparajith faced 174 balls for his 85 and is set to score his maiden Ranji hundred.
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He struck 10 fours and a six in his knock while Badrinath took 148 balls for his 61, which contained five boundaries including a six.
Brief Scores:
Tamil Nadu: 260 for two in 90 overs. (B Aparajith 85 batting , S Badrnath 61 batting; G Satish 1/1).