Without Haywood, the Mavs lost 88-86 as the Heat took a 2-1 series lead.
Haywood left Game 2 with a strained right hip flexor that he originally suffered during practice last week and aggravated during Thursday night's series-tying comeback win over the Heat. His participation in Saturday's practice and Sunday's shootaround consisted of stand-still shooting.
"I was hoping for a miracle," Haywood said Sunday evening. "It didn't happen. Hopefully I'll be ready for Tuesday."
Guard Rodrigue Beaubois, who lost his starting job in the regular-season finale and has not played a second in these playoffs, replaced Haywood on the active roster.
Dallas president of basketball operations Donnie Nelson has called Haywood the "unsung hero" of the Mavericks' playoff run. Haywood is averaging 3.3 points and 4.3 rebounds in 16 minutes during the playoffs. More importantly, he has served as a strong defensive backbone for a second unit that features a few scorers with defensive limitations.
Haywood said he has never had this type of injury, which especially bothers him when he attempts to sprint, which he hasn't done since pulling himself from Game 2 early in the fourth quarter. He hopes he misses only one game.
"I'm very optimistic because I've seen a lot of progression and it's gotten better every day," Haywood said, "but it's just about [if he can] go out there and do the things necessary to help the team.
"I waited 10 years to get to this point and then you're hurt, so it's definitely something you're disappointed about and very down about, but those are the chips that you get and you've got to play your hand."
Before the game, Mavs coach Rick Carlisle said: "It will change our rotation obviously. He's one of our biggest guys; we all know that. We got some different scenarios. Mahinmi will play some minutes, and then there's a possibility we could do some other lineups that will obviously be smaller, and we may have to adjust."
The Mavericks have not used a lineup without a traditional center often during the playoffs. When they have gone with that lineup, it has been horribly ineffective. The only time the Mavs didn't have Haywood or Tyson Chandler on the floor in the first two games of the Finals was a stretch of 1:43 in the fourth quarter of Game 2 when the Heat went on a 7-0 run.
"Ian just has to come out there and play with the same energy and that desire and that passion he shows in practice," Haywood said. "Everybody on this team is very confident in his abilities and we know that all he needs is an opportunity."
Chandler staying out of foul trouble is always a key for the Mavs, but that is especially true with Haywood out of the lineup. Chandler has fouled out twice in the playoffs and been in foul trouble in several other games.
"He's going to have to be aggressive but discreet about foul trouble," Carlisle said. "In these situations, he might have to play on the ground a little bit more."
Added Chandler: "I've just got to be smart about my fouls and situations. I've still got to be aggressive, still going to challenge shots. But going for pump fakes and all that stuff, I've got to be smart about that."
Tim MacMahon covers the Mavericks for ESPNDallas.com.