Gregor Townsend says he is "disappointed but not angry" after watching his Glasgow Warriors lose 25-16 to Northampton Saints in the European Champions Cup.
Glasgow prop up Pool 3 albeit after only one game following the cancellation of their match last weekend in Paris against Racing 92.
"You're angry with the players if they haven't put in the effort," he said.
"I firmly believed the way they were playing that we would win the game."
The Warriors, who trail pool leaders Saints by eight points, now play Scarlets back-to-back with the first match against the Welsh team at Scotstoun next month.
And Townsend, whose side have never qualified for the knockout stages of the Champions Cup believes the Warriors can break that record.
"To qualify from this group just got tougher," he told BBC Scotland. "You've got to win four or five games. We have five games left. But I believe we can still qualify from our group."
Asked whether he felt Glasgow would have to win all their remaining pool matches, Townsend replied: "Maybe four; we'll probably have to beat Northampton if it's four.
"Now that you've played a team, you find out a little bit more about them, you get a determination having put in a lot of effort and lost to put it right when we play them in January."
Back-row Josh Strauss, meanwhile, conceded Saints played the more intelligent rugby, piloted by stand-off Stephen Myler, and spearheaded by a bruising forward pack that dominated the set-piece.
"Credit to Saints, they played the game smarter than us," said Strauss. "That's where they got a lot of their advantage.
"At scrum-time, they're an excellent team. We looked at it all week, we knew what was coming and we couldn't counter.
"That's the disappointing thing - you do all the work; there's nothing more we could have done in training, it's the execution. If you're not there mentally with the discipline, it's not going to work."