NEW DELHI: Indian off-spinner Ravichandran Ashwin is adding a surprise leg-break to his already formidable bag of tricks but is convinced that the controversial 'doosra' cannot be bowled with a straight arm.

The 29-year-old is basking in the glory of a stellar year in which he won back-to-back man-of-the-series awards after spinning India to test series victories in Sri Lanka and at home against South Africa.

A slow bowler with a penchant for targeting the opposition's best batsman, his 'carrom' ball has outfoxed the best players of spin, including talismanic South African AB de Villiers.

Ashwin wants to add more variety to his craft and sees nothing wrong in an off-spinner bowling an occasional leg-break.

"I always keep trying things," the spinner told Times of India newspaper. "I feel if a batsman can play a reverse sweep, I can also bowl leg-break.

"With that thought, I have been trying the leg-break and I think I have mastered it now. But I will be sure when I unleash one in a match situation and take the top of off-stump.

"The next one is probably the googly and the flipper, but I haven't tried those," said the spinner, whose early success in the 20-over format earned him a one-day call-up before he established himself as India's main strike bowler in tests.

Ashwin has wreaked havoc on South Asia's spin-friendly tracks in the last six months, claiming 57 wickets in the eight tests he played at an average of 14.38.

While quite a few of them came from his carrom ball, Ashwin never had to bowl a 'doosra' -- the controversial delivery that spins the other way -- which has led to suspensions of several off-spinners from the region.

"Carrom ball is a proper knuckle ball and it can't be bowled with an offspinner's grip," Ashwin said.

"It is a finger-spinning ball and you don't use the wrist or elbow to bowl it... it's like a legal leg-break. But I don't think the doosra can be bowled without bending your arm, may be the topspinner but not the doosra."