What ails Rangana Herath?

Umbrellas occupy a special place in Sri Lankan culture. They are protection against torrential downpours that bear down like artillery shells, and are just as useful in the sun, which shines with homicidal intensity.

But by far the mightiest force of nature the island's umbrellas repel is the wrath of Sri Lankan parents. On Colombo's Galle Face green, in Galle's Fort, in any pretty, public place all over the nation, tens of thousands of them are deployed each day, as young couples titter behind them; their umbrella dipped low to conceal them in a semi-cocoon. They do not want to be recognised by someone who knows either family. If reports of their romance reach home, the paramours would endure any monsoon cyclone or dry-zone drought to never have to face their folks again.

South Africa have been hauling out a giant umbrella onto the ground for their batsmen, at every drinks break, but perhaps for the first time in Sri Lanka's cricket history, a giant umbrella was run out for the home team too, from the afternoon session onwards. These are conditions they are supposed to be familiar with, but after five sessions in the field, they were the more sapped outfit. Bowlers took an age to return to their bowling marks. Fielders practically had to be carried to their positions, in between overs.

Beneath the shade, one man in particular might have wished the big umbrella would have the same concealing effect millions of young Sri Lankan lovers seek from theirs. Rangana Herath finished the first innings with figures of 1 for 148. He has not had a worse first-innings return at Galle, since 2000, when he was almost another spin bowler entirely.

Herath delivered impeccable lines throughout his 60 overs, traveling at only 2.46 runs an over, but in the three years between the beginning of 2011 and the end of 2013, he had been so much more than just a line-and-length scrooge. He was a workhorse for sure, but the spearhead as well: miser and menace all in one, chipping away for long spells before bringing down the sledgehammer.

He had himself been Sri Lanka's giant umbrella of the post-Murali era, preventing the rest of a mediocre Sri Lanka attack from being washed away in Tests. He took 122 wickets at 25.27 in 23 matches in those three years, striking most remarkably in Galle, where he took 38 of those wickets, at 18.65. If there was a Sri Lanka win, Herath was almost invariably the pivot. In Sri Lanka's five Test wins after Murali and before this year, he averaged 13.97, had seven five-wicket hauls and three ten-fors. Kumar Sangakkara might have been bringing home runs by the boatload, but Herath was the matchwinner - just look at those numbers - how could you even argue?

But in a year in which Sri Lanka have won away thrice, Herath is yet to make his mark. Since the first Test of the series against Pakistan in the UAE, which started on New Year's Eve, Herath has averaged 42.65 in seven Tests. He has contributed, and even now, only the certifiably insane would even consider leaving him out, but he has not been the same old Herath.

The lull is not for a lack of heart - not least in the press releases that sometimes misspell his name this way. The fire still burns within, and sometimes roars in the open air when he takes a wicket. Moeen Ali charged and hit him for four over the offside in the Lord's Test, and when Herath bowled him next ball, he dipped down to one knee and shook his fists in a fit of angry delight. In another format, he delivered the individual performance of the World T20 when he blasted New Zealand into submission with 5 for 3.

The mind is as sharp as ever, as well. He is still weaving webs for batsmen, bowling one from wide out, a slider from in close, a dart here, a slower one there, and the odd carrom ball as well. But batsmen are just not getting out to him. He cannot apply the finishing bite.

Thanks in part to Herath's recent decline, Sri Lanka's attack is not finishing teams off either. The thrill of the finish at Headingley hid the fact that they needed almost 91 overs to take the last five wickets. Herath went into that day on a pitch offering moderate turn, and was expected to bundle England's tail out, but though he took three wickets James Anderson was resisting him with comfort towards the close.

At Galle, he would have hoped to carry the attack as he often has here, particularly with the injury to Shaminda Eranga depleting the hosts' resources. But almost every batsman who took guard on Thursday seemed more than capable of keeping him out. In only his fourth Test, Dilruwan Perera seemed the greater threat, even as South Africa's eighth and ninth wicket partnerships put on 75 and 66 respectively. JP Duminy's assessment of Herath's toil was almost condescending.

"You know what you're going to get with Herath," he said. "He's got great change of pace, but he hasn't got much variation. He doesn't give you anything." This is the top Test wicket-taker of 2012 he's talking about. A man who until very recently was the best-ranked spinner in the world

It is difficult to pinpoint exactly what is ailing Herath, but by process of elimination, perhaps it is the revolutions he puts on the ball. He has never been a big turner, but in England, Moeen would consistently rip it harder than Herath and often extract more turn as well, however misdirected many deliveries were. Herath was out-spun on day two in Galle again, by his colleague and by Imran Tahir. A few less revolutions than before is no trivial thing for a spinner, who relies on them not just for turn but for dip and drift as well. Maybe the chronic knee injury is taking its toll. He had had surgery on it this year, and perhaps he is pivoting a little more gingerly.

It is far too early to tell if Herath's plight is temporary or permanent. A fuller picture will emerge at the end of Sri Lanka's four home Tests over the next few weeks. He may even storm back in the second innings, and it is difficult not to wish he does. At his peak, he is among the most watchable purveyors of his art, and one of the most indomitable. But just when Sri Lanka's pace stocks are edging towards the light, their lead spinner seems to have retreated into the shade.

Herath is no shy sweetheart on a secret date. He wants to be up front and centre-stage, turning matches for Sri Lanka, just like he used to do.