The no-ball problem has plagued the SA legspinner in the first two Tests during the ongoing tour of England.
Johannesburg: South Africa leg-spinner Imran Tahir is "shocked" at his performance against England and is wondering how he has bowled as many as 17 no-balls during the first two Test matches of the ongoing series.
"I've never been a bowler who bowls so many no-balls and I'm shocked," Tahir told the daily Business Day on Friday from Derby.
"I just don't know what happened, but I need to check my action. The no-balls are the main issue at the moment from my point of view. I don't want to carry on like this. I need to improve," Tahir said.
Tahir claimed seven wickets in the first two Tests but was often found guilty of overstepping. During the second Test at Hedgingly, which ended in a draw after South Africa convincingly won the first match, Tahir was seen in regular and close consultation with bowling coach and former South African paceman Allan Donald.
Tahir is expected to be back on track with a two-day match against the county side Derbyshire, starting on Friday.
The Pakistani origin Protean cricketer has insisted that he will come back stronger in the final match of the series to help his team register a historic win.
South Africa are determined to clinch the ongoing three-match Test series, which will put them on the top of the ICC Test rankings, ahead of England.