Sackey was Wasps' try-scorer against Castres
Wasps: (16) 19
Pens: Staunton (3), Van Gisbergen
Castres: (6) 13
Pens: Ross (2)
Wasps were far from fluent but ground out victory over French side Castres in their opening Heineken Cup match on a wet afternoon at Adams Park.
The home side led 16-6 at the break after Paul Sackey's well-worked try lit up an otherwise attritional first half.
Castres hit back after the break with a close-range score from prop Akventsi Giorgadze but Mark van Gisbergen stretched Wasps' lead with a penalty.
Wasps ended the game strongly but lacked cohesion and execution overall.
Coach Ian McGeechan's men did at least become the first English team to win on the opening Heineken Cup weekend but they were unable to prevent Castres securing a losing bonus point for a defeat by seven points or less.
We know there are things we want to do better and it was ugly, but we stuck in there
Wasps coach Ian McGeechan
The drizzly, greasy conditions made handling difficult and both sides made early mistakes trying to move the ball wide.
Castres enjoyed the most of the early possession, if not the territory, as the workmanlike opening 40 minutes was punctuated with three penalties for Wasps' first-choice fly-half Jeremy Staunton and two from the visitors' former Leeds stand-off Gordon Ross.
But Wasps broke the stalemate on the brink of half-time when left wing Sackey took a short inside pass from scrum-half Eoin Reddan and sliced through the French defence close to the still-bound scrum on the 22 to score under the posts.
Castres refused to buckle and came out fired-up for the second half, stinging Wasps quickly with a close-range score from Giorgadze after an attacking line-out close to the line had the home side in disarray.
Wasps looked out-of-sorts in some of their midfield organisation and defensive systems, and Castres playmaker Ross began to exert a significant impact on the game.
Lewsey (left) limped off with a hamstring injury
As Wasps centre Josh Lewsey limped off injured, Castres set off on a flowing break down the blind side and were held up on their first attempt to breach the try line.
They won a penalty and opted for a scrum but Wasps, to their credit, snuffed out the attack.
McGeechan swapped Staunton for King with just over 20 minutes left and the fly-half immediately began to pump balls in behind Castres to test the French defence.
Castres tried two speculative drop-goals in quick succession but the lack of accuracy was punished when Wasps took three more points from a penalty after going close to the try-line following a turnover and breakout from their own half.
The six-point cushion gave Wasps the confidence to close out the match but their decision-making and tactical nous left much to be desired.
Wasps' next match is on 28 October at Perpignan, who opened their campaign by claiming a bonus point from a 25-10 win against Pool One makeweights Treviso.
Wasps coach Ian McGeechan:
"We know there are things we want to do better and it was ugly, but we stuck in there.
"In the first half we got the control we needed, but in the second the conditions deteriorated and we didn't have that control.
"We had to play for 25 minutes in our own 22 and apart from one moment - and the players aren't sure about their try - we held up well.
"Our discipline was good and in the last 10 minutes we didn't give the initiative back to them. In previous games, we might have done that."
Wasps: Van Gisbergen; Sackey, Lewsey, Waters, Voyce; Staunton, Reddan; Payne, Ibanez, Vickery; Shaw, Palmer; Leo, Rees, Dallaglio (capt).
Replacements: Ward, Bracken, Skivington, Haskell, Amor, King, Erinle.
Castres: Teulet; Milford, Christophers, Carballo, Fleming; Ross, Laussucq; Giorgadze, Terrain, Castex; Pape, Nallet (capt); Bias, Tabacco, Faure.
Replacements: Roumieu, Saayman, Ghezal, Fourcade, Canavosio, Wisniewski, Moffat.