Rhys Ruddock admitted Leinster were caught cold in the furnace of Stade Ernest-Wallon as a pumped-up Toulouse bloodied the nose of the reigning European champions.
Maxime Medard's scintillating breakaway try 12 minutes from time swung a thrilling Heineken Champions Cup Pool One encounter, as the hosts held on for a 28-27 victory.
For a team not used to losing, it was a bitter pill to swallow, but Ruddock was gracious enough to admit that the province only had themselves to blame as they wilted in the face of a doggedly tenacious home performance.
RECAP: TOULOUSE 28-27 LEINSTER
"It's hugely disappointing," he told RTÉ Sport's Michael Corcoran.
"Credit to Toulouse, I thought they were really good. They'd a strong, fast start like we've seen in all their home games this season.
"We knew what to expect but we just found it hard to stop. We've probably got to look at ourselves and the level we brought, and also there were a few mistakes.
"We knew what was coming, but it's another thing when you get over here with the crowd in France and the passion they bring to it."
After a poor start it looked like Leinster had steadied the ship as Sean O'Brien's try left them trailing 14-13 heading for the break. Sofiane Guitoune struck back a minute before half-time however, and even after James Ryan and Sean Cronin touched down Toulouse still wouldn't crack, with Medard having the final say.
"We played well at times," added Ruddock.
"The longer we held on to the ball the more we looked like we could create opportunities. But that's probably why some of the inaccuracies of giving the ball away hurt us a bit.
"Even allowing them to run it our from their own 22 and things like that where they came alive and put the pressure back on us.
"We had our hearts set on coming over here and getting a win. We were under no illusions it would be a hugely tough challenge, one of the toughest a lot of us would ever have experienced. We couldn't quite get over the line."