So what exactly is the knuckleball?
For starters, contrary to the name, the knuckleball is a delivery gripped not by the knuckles but by the fingernails. It is a variation of the slower delivery but one with hardly any rotational spin that wobbles and dips before reaching the batsman. Since the wrist isn't whipped while delivering the ball, it hangs in the air like a full toss before dipping suddenly. No one can predict how the ball will behave after the bounce. Normally, since there is no backspin, a knuckleball delivery doesn't turn much but then again, it sometimes might if there is any air-flow around the stitches.
The delivery was developed first in baseball, with the fingernail grip used to eliminate spin from the delivery. Eddie Cicotte who played for Chicago White Sox is regarded as the pioneer of the knuckleball. He was nicknamed Knuckles in 1908.
So how did it find its way onto cricket pitches?
Well, flatter pitches, thicker bats, batting powerplays and fielding restrictions have turned cricket into a batsmen's game. 400 has become a regular score in ODIs while 200 is now a chaseable target in T20s. This has brought in the dire need for variation in bowling and as far as Indian fast bowlers are concerned, knuckleball seems to be the answer.
As mentioned earlier, Zaheer was the first Indian pacer to use the knuckleball technique at the international stage. It was on display at the 2011 World Cup. He perhaps picked it up from his Royal Challengers Bangalore teammate Charl Langeveldt. More recently, Bhuvneshwar seems to have picked up the technique rather quickly and is using it to good effect.
The difference between Zaheer and Bhuvi's deliveries is how they hold the ball. Zaheer used to bend his forefinger behind the ball and sort of flick it when releasing it, slowing down the delivery and making it skid on the pitch. Bhuvi on the other hand holds the seam with the fingertips of his index and middle finger, making his deliveries wobble and hang in the air slightly longer than Zaheer's.
Bhuvi used the technique to good effect in the recent series against South Africa. In the first T20 in Johannesburg, he returned with figures of 5/28, becoming the first India bowler to pick up a fifer in all three formats.
"I have been bowling that knuckleball with the seam up since the last one year. I worked on it in the IPL. Batsmen are quick to size you up and hence you need to keep evolving and reinventing oneself,” said Bhuvi, after the match.