The Heat let their foot off the gas when reigning league MVP Giannis Antetokounmpo reinjured his right ankle early in the second quarter of Sunday's game.
"Well, it shouldn't affect ours, but I think that we relaxed a little bit," Butler said when asked if the Heat's play changed after the Bucks' big man exited. "And we stopped playing basketball the right way. We stopped guarding. We stopped living by our defensive principles. We weren't getting 50-50 balls. We were getting outrebounded. It was just all bad."
The Heat still have a commanding 3-1 lead in their Eastern Conference semifinal series, but Heat coaches and players were frustrated by the fact that they couldn't end the series the day the Bucks lost their best player.
"I feel like we played like we were up 3-0," Heat All-Star big man Bam Adebayo said. "That's not giving enough effort, not sacrificing our body, and we ended up losing because we were up 3-0. They're a good team. So at the end of the day, we should have played like we were in Game 1, Game 2 and Game 3 ... I feel like we didn't play a maximum effort the whole game."
The Heat's inability to finish is surprising, given how mentally tough the team has played throughout the bubble. The Heat came into the game 7-0 in the postseason, confident in the belief that their businesslike culture would keep them focused on the task at hand.
After Antetokounmpo went down, Bucks forward Khris Middleton and his teammates continued to play hard and pushed a Miami team that appeared to lose some of the focus that has defined the group's stay at the Walt Disney World Resort campus.
"We didn't have the mentality just to take the win," Heat forward Jae Crowder said. "I don't know if Giannis going out was a dictative factor for us, but we just didn't have the same mentality."
The Heat refused to use Antetokounmpo's injury -- or several questionable calls down the stretch -- as the reason they lost the game, repeatedly giving credit to an undermanned Bucks team -- specifically when asked about the officials' review with 1:44 left in regulation and the Bucks leading 106-104. Butler was clearly fouled by Eric Bledsoe, but the play was not challenged by Spoelstra, and the officials couldn't enforce a post-replay foul call because that is not an option in the current NBA rulebook.
Butler did not want to use the sequence as an excuse. He said he did not get an explanation from the officials.
"I just got to be stronger with the ball, hold on to the ball," Butler said. "That's fine. On to the next play, and I think we did a great job of that. We just didn't win the game. There were way too many things that we did wrong that we just can't let happen."
Spoelstra, who has said repeatedly throughout the season that he does not like the coaches' challenge that was implemented before the season began, did not want to use any call as a reason the Heat didn't close.
"It's so complex," Spoelstra said. "It's so confusing. And there's a ton of gray area with it. There's still so many opportunities, kind of a loophole gray area for it to slide through the cracks. Whatever. We can't beg our way or challenge our way to win this series. They really deserved to win this game."
When asked if he'd like to see the rule changed so that officials can make a call after a replay review isn't made on the floor, Butler demurred.
"Nah, I'm cool," Butler said. "We didn't deserve to win that game. We didn't play our type of basketball. That play is just another play out of so many. They call that a foul or whatever -- something else bad probably would happen the way that we were playing tonight. So we just [need to] be better and not have to rely on one call to change the game."
The same goes for the block call on veteran Heat guard Goran Dragic with 1.9 seconds left in regulation. Spoelstra decided not to challenge that before Bucks guard Donte DiVincenzo went to the free throw line and hit one of two to tie the game at 107.
"Look, maybe we could have stolen it with one of those challenges and have the officials bail us out," Spoelstra said. "We did enough things, and they did enough things. I don't want to take away credit where it's due."
Butler and the rest of the Heat players remain confident that they can close out the series on Tuesday in Game 5, but the sting of letting their foot off the gas will motivate them over the next two days.
"I think that was it," Butler said of the letup in mentality. "We did what we always say we can't do, which is get comfortable. We thought this one was going to be easy, and it was not. ... We knew what we had to do coming into this game, so going into the next one, we just got to put them away."