NSW Waratahs' Super Rugby title defence is hanging by a thread after their second defeat at home this season again exposed a major chink in their attacking armour.

The Stormers fully deserved their 14-point win at Allianz Stadium as, led by veteran back-rower Schalk Burger, they used a similar game plan to that which saw Western Force upset the defending champions in the opening round. The South Africans stung the Waratahs on the counter while the Force preferred to grind away through the forwards in what remains their only win of the season; but what both sides did so well was to let the Waratahs beat themselves. And that problem reinforces one major fact for the Waratahs: they appear to be one forward short in 2015.

Kane Douglas' departure was always going to leave a hole in the Waratahs - and from the look of it the Wallabies, too - and Michael Cheika, to his credit, tried to go out and plug that gap with the recruitment of young Warriors forward Sam Lousi. But the young New Zealander was injured against the Blues, and he was only going to be a Band-Aid solution for a serious wound anyway.

So much of the Waratahs' success in 2014 was built around their forward pack: the likes of Kurtley Beale, Israel Folau and Bernard Foley earned the plaudits, but everyone knew the hard work was being done up front. They had the luxury of using Will Skelton or Jacques Potgieter off the bench, often with devastating impact in the second half of matches, but that is no longer possible after Douglas' departure and the South African recruit and Wallabies hopeful have been nowhere near as effective this season. The duo's handling has also left a little to be desired.

Jacques Potgieter is nowhere near as influential in 2015 © Getty Images

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And opposition teams have discovered this season that the Waratahs will eventually become their own worst enemy if you are a little more selective in the breakdowns you attack.

On Saturday night, the Stormers largely left Burger to be their lone breakdown warrior. The South Africans were happy to let the Springboks hard man attack one out of every three or four stoppages, leaving everyone else to set the defensive line.

Time and time again the Waratahs tried to go around the Stormers, but the visitors, with their line set, had little trouble in picking off the hosts' backs - Beale in particular coming in for some serious punishment throughout the 80 minutes.

The Waratahs did manage two tries but they were scored in opposite corners - a testament to the outstanding defence of the Stormers. The visitors also forced 19 turnovers and held their hosts to just six clean breaks. Late in the game, the Waratahs held the ball for well over 20 phases but at no stage did the Stormers line bend - let alone break.

Michael Cheika's game plan relies on front-foot ball brought about by a hard-running forward pack. But he's down one key soldier this season and, with no quick fix anywhere in sight, a second straight Super Rugby title looks to be nothing more than a pipe dream.