They face the Chiefs in their last regular-season game on Saturday, and during the week, their motivation would be to win that game and prospectively take first place.
"It's important the character the group shows now. The leaders will stand up and say we're going into the playoffs soon, so we need to sort a few things out."
The Crusaders gave themselves a mathematical chance of making the playoffs, although that will depend on other results.
Cotter said he was confident that if the Blues met them again at Eden Park, they would perform better.
"They [the Crusaders] played well, but I think we can get better."
Cotter said it was a good contest, and the Blues had come off second best.
"It'll give us an opportunity to have a really good look at ourselves over the next week before we get the Chiefs at home."
The Blues will take the loss on the chin and have to improve for the remainder of the season.
There were several reasons for a loss, including an accident, a refereeing decision, an attitude, or technically and tactically not getting things right.
"If we look at today, we didn't control the game particularly well because we didn't have the set-piece we wanted. We have to work on that. We gave away too many penalties and gave the Crusaders access.
"We accelerated well three times and scored and then gave them a try straight back. We couldn't break away; we couldn't get the lead from them, and, in the end, they finished strongly.
"They finished on our line and, credit to our guys, we didn't let in a try. That was a great bit of character. It was tough; we had to defend a scrum, and they'd probably been reasonably dominant over that part of the set piece, and the guys [got] stuck in and didn't give away a try.
That was important because they at least gained a bonus point that allowed them a share of the competition lead.
Cotter said it was hard to accept being out-passioned.
"We thought we'd done enough and it wasn't enough. And those are things we need to learn from, especially coming to knock out rugby. You've got to be locked in for 80 minutes or more."
While captain and lock Patrick Tuipulotu had put his hand up, Cotter felt the Blues were a second slow at times around rucks and clean out.
"We were watching rather than acting, and there was half a second when the Crusaders were very good. They were hungry, and they turned up around the collision area. We couldn't get fast ball.
"We still managed to score but probably the most disappointing part of the game will be the set-piece and the fact that when we scored and got in front, we let them score straight back in."
He said the loss of Stephen Perofeta when he was sin-binned for a deliberate knockdown during an attempted intercept had been ironic because the Blues scored when reduced to 14 men.
"We played better when we had 14 players on the paddock. It sort of lifted the guys which was ironic."
The incident would be reviewed, and something good or bad would come from it.