EUROPEAN CUP/CASTRES v LEINSTER:LEINSTER COACH Michael Cheika conducted a brief post-match inquisition with his team behind a closed dressing room door for several minutes but reappeared to offer his observations on a bitterly disappointing night for the Irish province at the Stade Pierre Antoine.

Leinster's 18-15 defeat means that their next Heineken Cup assignment, in January at Twickenham against Wasps, is likely to decide pool honours, a state of affairs that seven days ago would have been unthinkable.

The disappointment at the failure to secure a bonus point at the RDS last Saturday against the same opposition paled into insignificance compared to last night's setback. Wasps play Edinburgh at Adams Park tomorrow and if they manage a bonus point they'll move to 13 after four games, just two adrift of Leinster who must travel to face the English club at Twickenham.

Cheika admitted: "It's a straight shoot-out now and we can't afford to lose another match in the pool.

"If you take your eye off the ball (in terms of performance) then you get beaten. We have got to get our game back to the level that we had it for the first two matches.

"We are not going anywhere until we get more solid," a reference to Leinster's facility to vacillate between the excellent and the rank in their pool outings to date.

Cheika continued: "We play really well one week and then are not as consistent the following week. They outplayed us at the rucks and it cost us in this area. They were able to turn over ball at the breakdown and that meant we couldn't get the continuity that might have opened things up further out.

"We didn't kick well enough to get the right sort of field position that would have allowed us to exert consistent pressure.

"We scored two tries when we played the game we wanted but other than that made far too many mistakes. This put us on the back foot and we left ourselves vulnerable.

"We incurred the wrath of the referee too many times. The ruck area was definitely a problem as they poured numbers in and we were beaten. We weren't sharp enough but still had opportunities to win the match. It came down to too many simple errors and when you do that you're always going to be vulnerable. It also meant that we couldn't get the scores that might have given us the impetus to kick on from that point."

Leinster appeared racked by indecision at times and, once again, in keeping with the ill-judged kicking game at the RDS they made things far too easy for Castres.

The French side were average on the night and they too slavishly adhered to the up and under but crucially it was their ability to compete at ruck time and the turnovers they manage to force in contact that ultimately proved decisive.

Leinster must now regroup quickly and somehow rediscover the quality of performance that was a feature of their victory over Wasps at the RDS. From being in a position of strength, their pool ambitions rest squarely on their ability to travel to London and win. Mathematically there are other permutations but it is difficult to escape the feeling that for the team to re-establish their credentials it has to be done on their next outing in European competition.