Opting to bat first, Delhi received an early jolt when Shalabh Srivastav removed opener Shikhar Dhawan (6) but Chopra and Mayank Tehlan (25) put on 61 runs to steady the innings.
Praveen Kumar broke the partnership by trapping Tehlan and after another eight runs were added to Delhi's total, the lanky pacer struck again by castling host captain Manhas. Delhi found itself in morass at 79 for three.
Viraat Kohli (42) then joined Chopra to stem the rot and put on 84 runs for the fourth wicket as the hosts cruised to 143 when Rohit Srivastav's direct throw from square leg caught Viraat short of ground.
Next man in Rajat Bhatia (32), however, played sensibly and he, along with Chopra, guided the team to 179 for four at tea.
After the new ball was taken, Praveen Kumar again came up with a two wicket burst in the 85th over to deny Delhi a clear upper hand in the match.
He first uprooted Bhatia's leg stump with the second ball of the over and then trapped Vijay Dahia for a three-ball duck to reduce the hosts to 245 for six.
Chopra's patient and cultured, unbeaten knock of 128 was the result of more than six hours' of patience during which he faced 269 balls and had 14 hits to the fence.
He square-cut leggie Piyush Chawla to reach his century in 222 balls and had hit 10 boundaries by then.
In the final session of the day, Chopra stamped his class by hitting spinner Shivkant Shukla for successive boundaries -- the first being an exquisite straight drive, followed by an impeccable on drive.
The unassuming opener later denied that the ton, his 16th in first class cricket, was a message to the selectors who preferred his teammate Gautam Gambhir over him for the Test series against South Africa.
''It was a very dear knock for me and I'm happy that I played a chanceless knock. But it was not any message for the selectors.
''They have picked Gautam over me and I wish Gautam all the best,'' Chopra added .Chopra's name came up for discussion in yesterday's selection committee meeting but fellow Delhi opener Gambhir got the nod in the end. Commenting on today's proceedings, Chopra said, ''We were in a very strong position before Praveen came up with a late burst and to be honest, we can't dictate terms tomorrow.
Now the idea would be to go tomorrow and get as many runs as possible.'' Asked how he felt after he was dropped from Team India, Chopra was candid enought to admit, ''Like every other human being, I too felt bad after being dropped. I have been trying too hard in the last two season but this time I'm more relaxed and the result is showing,'' he added.
Delhi 257 for 6 (Akash Chopra 128 n o, Virat Kohli 42, Rajat Bhatia 32; Praveen Kumar 4 for 53, S Srivastava 1 for 51) Vs UP