Shane Williams says Ospreys' Pro12 final win over Heineken Cup history-makers Leinster proves the Welsh team are among Europe's best teams.
The wing, 34, ended his Ospreys career with two tries, the second helping earn the dramatic win as fly-half Dan Biggar converted for a 31-30 win.
A week earlier, Leinster became the first team to seal three European crowns in four seasons.
"We've shown that we can compete with the likes of Leinster," said Williams
"They are probably the best European side ever, really, up there with Toulouse and Munster.
"And we can come to the RDS and play a full-strength side and come away with a victory under pressure.
"That's the sign of a good team.
"Everyone alludes to the Heineken Cup all the time, but we've shown it's a tough competition, playing the best teams in Europe and some of them are the best teams in the world - it's tough."
Ospreys bowed out in the pool stage of this season's European flagship tournament.
That disappointment was followed by a back-room reshuffle midway through the season with head coach Sean Holley and director of coaching Scott Johnson departing.
Former flanker Steve Tandy took over as head coach and Ospreys produced some scinitalating displays on their way to the Pro12 final, memorably beating Munster 45-10 in the semi-finals.
Williams, who appears against Wales for the Barbarians in Cardiff on Saturday, 2 June as part of his farewell to the game, admits Ospreys made mistakes against Leinster.
The visitors to Dublin conceded what they considered "sloppy" tries by Isa Nacewa and fell foul of some refereeing decisions they disputed.
Williams added: "We'd been showing glimpses that we can play some rugby in that game, but a little bit frustrated by some decisions, some mistakes, letting a few sloppy tries in and uncharacteristic really.
"And we had to play better in the second-half and it's as simple as that.
"The effort has certainly been there all season and it was from the first-half and fair play to the guys, they just gave it their all right to the end again.
"It was commendable from the guys."
Williams' two touchdowns played a significant part in that effort, but he was determined to make a mark.
"That's what I'm here to do and even though it was my last game I knew that I wanted to get involved in that game," said Williams.
"Again, I found it very frustrating, but I'll keep playing right to the end and if there's an opportunity I can sniff it - that's what I'm there to do.
"We seemed to be giving it away most of the time as well with some sloppy tries…a couple of bad decisions, discipline at the start of the second-half.
"We got a great try by Becky [centre Ashley Beck], but then we gave away three penalties in a row. It just didn't look to be going our way.
"But the guys stuck at it right at the end.
"And we've worked hard this year. We've had a lot of ups and downs, a lot of changes in the camp and we've turned it around.
"So fair play to the boys.
"I've had a great time with the Ospreys and what a fantastic way to hang my boots up."