Ospreys director of coaching Scott Johnson has come away from the Stade Felix-Mayol frustrated as the Ospreys went down to a late Paul Sackey try in their opening Pool 3 game.
The Welsh side have reached the knock-out stages of Europe's premier competition for the last three seasons and were on course for an important victory away at Toulon until England Internationals Jonny Wilkinson and Paul Sackey combined to take the win.
"We won't know the proper measure of this result for a couple of months," said Johnson.
"It was frustrating for us and there was some naivety on our part.
"We couldn't hold field position all day long, didn't have many attacking line-outs and Toulon didn't play rugby.
"I was falling asleep and it was hard to play against. But that's the way they play.
"But we have to work hard, be honest with ourselves and come back next week.
"It's a difficult pool but this result won't become clearer until a later date. We will take the one point away with us and move on."
The Ospreys welcome London Irish to the Liberty Stadium next weekend who beat double Heineken Cup champions Munster in the other opening Pool 3 game.