Wing Shane Williams admits the Ospreys' performance in their 26-26 Heineken Cup draw at Treviso was "strange" in some respects.
The player who bows out of Test rugby when Wales face Australia on 3 December also says the outcome was "hard to take".
Teenage fly-half Matthew Morgan levelled in the dying moments with a long-range penalty.
"We made far too many mistakes in crucial areas," said veteran Williams.
"Discipline in the first-half was quite poor - little, silly penalties that kind of takes the wind out of your sails at times.
"It was very frustrating and, of course, the tries that we conceded were all from our mistakes."
But Williams was equally unhappy about the Ospreys' attacking failures even though they did enough to stay top of Pool Five as Biarritz beat Saracens.
He said: "We broke the line several times - there was good support to begin with, but we got close to try lines and then almost didn't look threatening when we got behind them, really.
"And that's strange - disappointed there, but there's a couple of things we know we can be better at.
"And the disappointing thing is that we made critical errors that have cost us tries and a lot of three points [penalties] have been handed to them on a plate at times.
"And you can't afford to do that in the Heineken Cup wherever you're playing."
However, Williams was pleased Biarritz beat Saracens in Pool Five, even if the English club gained a bonus point against the Basque club, who the Ospreys beat in the opening round.
He said: "We knew [Pool Five] was going to be very, very tight anyway and, probably, the score suited us today with Biarritz [winning] obviously.
"We probably would have preferred Saracens not to get the bonus point, but we knew this group was going to be tough and I'm sure we'll see Treviso with a few more scalps in this competition.
"But it's difficult to explain. We've worked very hard since the Biarritz game on things we felt we had to improve on and we didn't quite do it today.
"So that's hard to take, but at least we know we can play a lot better.
"We got out of jail in the end, but we're disappointed we didn't put that game to bed.
"But it's never easy to come to Treviso. They are a side that's progressing each year."