The Bulls go into Tuesday's game against the Raptors at the Air Canada Centre having won 11 in a row against Toronto, including twice this season.
The answer, Casey feels, is provided by the way the Raptors dominated the Indiana Pacers 116-91 Sunday night.
"From start to finish, I thought it was a solid contribution offensively and defensively," Casey said. "Set the tone defensively from start to finish from the jump ball. That's the way we have to play and continue. Whatever we have to do to get this (monkey) off our back against Chicago, they beat us 11 in a row and that has to stop. Collectively, whatever we have to do defensively and offensively to set the tone, we have to do that."
The Raptors (41-29) came close Jan. 7 when they blew a 19-point lead and went to overtime before losing 123-118 at Chicago. The Bulls won 105-94 on Feb. 14, also at Chicago. The game Tuesday is the finale of the season series.
The Bulls (33-37) need to maintain their streak against the Raptors as they try to make earn a spot in the Eastern Conference playoffs.
They have played the past two games without Dwyane Wade, who will miss the rest of the regular season with a fractured right elbow.
The Bulls defeated the Utah Jazz 95-86 on Saturday at the United Center, after losing 112-107 to the Wizards in Washington Friday.
"It's got to be a total team effort," coach Fred Hoiberg said.
Jimmy Butler can see progress as the team adjusts to playing without Wade.
"It started off a little shaky," Butler said. "But we started to fix a lot of things in that second half (Friday). And I think that's the way we're going to go moving forward. We've got to keep things really simple. We can't put too many guys in too many places and positions on the floor, because they're not used to it. And it's not their fault."
Butler scored 23 points against Utah. Bobby Portis had a career-high 22 and rookie Denzel Valentine scored 11 and grabbed 12 rebounds.
Robin Lopez, who is averaging 10.3 points and 6.5 rebounds, has averaged 19.5 points and 8.5 rebounds in the past two games.
"I know there's a lot on Jimmy's shoulders," Lopez says. "The defense really keys in on him. I'm just trying to be a bit of a pressure release in any way I can. A lot of the guys are doing a great job in stepping up in that regard."
The Raptors regained their eye for shooting 3-pointers against the Pacers, going 12-for-27 from beyond the arc, led by four from DeMarre Carroll.
It was the first time since March 3 at Washington that Toronto had hit double-digits in 3-pointers, a span of seven games.
'It's just knowing that the ball is going to get swung," said DeMar DeRozan, who scored 22 points and was 1-for-2 in 3-pointers Sunday despite not playing in the fourth quarter of the one-sided game.
"Just finding a spot and everybody being conscious of moving the ball. If you have a good shot, look for the great shot. I think that's what we have been conscious of and guys being ready to shoot.
"The key is I thought they were in the rhythm of the game, it wasn't forced, it was natural and that's what we needed," Casey said.
Jonas Valanciunas had 11 points and 13 rebounds Sunday to record his career-best 26th double-double of the season, which also leads the team.
The Raptors are 23-12 at home and the Bulls are 13-22 on the road.