After conceding a vital 61 run lead to Sri Lanka A, South Zone fought back in style with Uthappa and Dinesh Karthick sharing a 167-run first wicket partnership to demoralise the visitors.
Uthappa's 141 came off just 191 balls with 14 boundaries and one six and Karthick made a composed 95 with 11 hits to the fence, making a mockery of the Sri Lankan attack though Akalanka Ganegama looked impressive in short spells.
After Dinesh got out, Uthappa was involved in another fruitful 125-run second wicket partnership with captain VVS Laxman, who scored 45 runs.
Late in the day, Rayadu fell for 17 runs to give Sri Lanka A lucky fourth wicket.
Akalanka Ganegama, whose spell read 21-2-82-4, claimed all the wickets.
South Zone 266&333 for 4 ( Robin Uthappa 144, Dinesh Karthik 95, VVS Laxman 45, Venugopal Rao not out 19; Ganegama 4 for 82) Vs Sri Lanka 'A' 327 all out ( Thilan Samaraweera 69, Chamara Silva 70, J K Silva 55, ML Udawatte 34, Jehan Mubarak 32; Kaushik Reddy 4 for 57, Yo Mahesh 3 for 74, Sreesanth 2 for 75)