'We also largely need to direct our success to Ravindra Jadeja because he kept one end tight.'
In the recently-concluded five-Test series against England, which India won 4-0, Ashwin picked up a whopping 28 wickets besides scoring 304 runs.
"There is no doubt that Ashwin is the best striker bowler we have. He is the best spinner in the world now," Prasanna said on Thursday.
However, the 76-year-old advised Ashwin to flight the ball more often which would make him even more dangerous.
"Unless and until he makes the batsmen step out and drive it will be a little difficult for him. In the back of his mind he has got a leg break which he thinks is very effective.
"But watching him, the batsmen will easily know that he is going to bowl that delivery. From his action you can easily find out that he is going to bowl that one."
Prasanna was part of the famous Indian spin quartet of the 1970s that also included Bhagwath Chandrasekhar, Bishan Singh Bedi and Srinivas Venkataraghavan.
Prasanna, who played 49 Tests in which he claimed 189 wickets from 1962 to 1978, had words of appreciation for left-arm spinner Ravindra Jadeja.
"We also largely need to direct our success to Ravindra Jadeja because he kept one end tight (against England). These two have largely contributed to our series win against England."
Known for his mastery over flight, Prasanna further said on Jadeja, "Now Jadeja has come to a stage wherein he can read the mind of batsmen and turn out to be a strike bowling match winner."
Prasanna feels young all-rounder Jayant Yadav's spin bowling is not cut out for Test matches.
"If you really ask me Jayant Yadav, I do not think, he will be able to bowl long spells at all. He is an useful batsman for T20 or one-day matches and he can bowl good four overs in these two formats."
"...He has already proved that in longer version of the game, he is not a strike bowler. He is not meant to be strike bowler."
Image: Ravichandran Ashwin bowls.
Photograph: BCCI