Muttiah Muralitharan has been Sri Lanka's go-to man for several years now, but over the last three years he's had to work much harder for his wickets. He finished the Ahmedabad Test with match figures of 3 for 221 from 63.5 overs, of which only one victim was a top-order batsman. Equally worrying was his lack of bite on the last day, admittedly in conditions which offered little assistance for bowlers. It's only the seventh time he finished wicketless in the second innings, but the first time this happened after he bowled more than 20 overs.

It could be dismissed as a one-off, except for the fact that Murali's form has been on the decline since 2007, especially when playing away from home. His overall stats during this period are still respectable - 112 wickets in 20 Tests at 26.51, with nine five-wicket hauls - but dig a little deeper, and cracks begin to appear.

Of his 112 wickets, 39 have come in five Tests against Bangladesh, at an average of 14.46. Take away those numbers, and his overall average during this period climbs to 32.95. Even that average has been propped up by his numbers at home; overseas, he has only taken 20 wickets in seven Tests, each costing him 60 runs. To be fair to Murali, some of those matches have been played on the flattest featherbeds - earlier this year, for example, when Sri Lanka toured Pakistan, the first Test in Karachi yielded 1409 runs for the loss of 13 wickets in the two first innings.

What is equally surprising, though, is Murali's lack of effectiveness in the second innings of Test matches during this period. He has bowled in 17 such innings during this period, but has only taken 45 wickets, at an average of more than 32, which is ten runs higher than his first-innings average.

More than once, Murali has been lethal in the first innings, but far less effective in the second. In Port of Spain last year for example, he took 5 for 79 as West Indies were bowled out for 294 in the first innings. In the second, with West Indies chasing 253 for victory, Murali returned disappointing figures of 1 for 92 as West Indies won by six wickets. Against Bangladesh later that year, he claimed 6 for 49 in the first, but toiled 48 overs to take 4 for 141 in the second.

After the Ahmedabad Test, Murali averages 31.47 against India, one of only two teams against whom his average tops 30 (Australia is the other). In India the average goes up to 42.58, with 34 wickets in nine Tests. The only country where his performance is worse is in Australia - an average of 75.41, with 12 wickets in five Tests.