The extent of feelings he has for Sai...is Pakhi!
She has only one duty in CN, observe Virat and monitor him. Out of her obsession for him, she observes his thoughts and reactions more than anyone else, even Virat himself. She has seen him falling in love with Sai more clearly than anyone. She cries when Virat is with Sai because, his every move screams love for her. She knows he is beyond retreating back. She senses his reactions much better than Virat himself, and estimates exactly how much he will react. Latest example being her plan to place AJ with Sai. She has already used every weapon against Virat, latest incident being the last one. Failing there, now she will focus more on Sai. But the problem is she doesnt understand Sai, does she? :) So she will falter, I guess....
Disclaimer: Dont MU me for bringing Pakhi. But this is my observation. :)