India have raced to 371 for four after the opening day, looking set for another big total.
Asked if off-spinner Perera, who has pipped Muttiah Muralitharan to fastest 100 wickets for Sri Lanka in 25 Tests, is under the pump for the first time because of the quality of batsmanship, Ratnayake said: "Everybody knows that Indian batsmen are at a different level but having said that, it's not an excuse.
About young Sandakan, Ratnayake felt that lack of confidence did not allow him to bowl the 'googly' (chinman's away going delivery to right-hander) to centurions Murali Vijay and Virat Kohli.
"He is comfortable with his normal chinaman deliveries (bringing back into right hander) but the googly is the thing that we see might trouble the batsmen which he hides very well. It is not very easy to read. He should bring it on and mix it.
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Ratnayake also revealed his team's defensive mindset going with extra batsman which has put enormous load on the bowlers.
"It was a decision which we had to take. We had to decide whether to go with an extra bowler or with an extra batsman since we hadn't done well in our batting. We wanted to make a better statement with a better score. If we were going to bat the first day, we wanted those seven batsmen. That was the decision we had to take.