Udonis Haslem looked exhausted as he sat in the Miami Heat's locker room late Tuesday. After bending over to take off his shoes, he exhaled a long sigh of relief. The thought of practicing on Wednesday? Nope, that wasn't going to happen. All Haslem wanted was to soak in an ice bath in hopes the deep cold would rid him of his pain.

That's what guarding Dallas Mavericks forward Dirk Nowitzki will do to you, especially when you're trying to play on a sore left foot. And yet for nearly 30 minutes of the Heat's 92-84 victory in Game 1 of the NBA Finals, Haslem looked as sturdy as ever. Nowitzki scored 27 points, but Haslem helped make him earn them: Nowitzki missed 11 of his 18 shots.

The majority of attention on the Heat during these Finals will understandably be focused on their three superstars: LeBron James, Dwyane Wade and Chris Bosh. But Haslem's defense on Nowitzki – just like it was five years ago – will go a long way in determining whether Miami wins its second championship.

"It ain't easy," Haslem said. "After the game you can feel it. There's not too many [power forwards] running off [screens]. Usually a four-man gets a cross screen to the post or something like that. They run him off singles …"

Haslem didn't finish the sentence, exhaling one more time instead.

"It's difficult," he said.

Haslem took a keen interest in watching Nowitzki on TV during the first three rounds of the playoffs. The 7-foot Nowitzki's ability to shoot 3-pointers after coming off screens typically reserved for guards, the one-legged fallback jumpers, the pretty baseline spin – Haslem loved it all. But with each passing playoff game the Heat and Mavericks won, Haslem went from watching Nowitzki for fun to watching him as preparation.

"I was doing my homework from the beginning of the playoffs," Haslem said. "I didn't know if we were going to play them. But when I saw him playing the way he's playing throughout the playoffs, I'm a basketball head so I love watching games. I've been a fan of his all the way up until this point. I kind of started my work earlier without really working – just watching him play."

The fact that Haslem is even guarding Nowitzki is impressive in itself.

Haslem was expected to be a key role player for Miami, but missed the majority of the season after tearing ligaments in his foot on Nov. 20. He didn't return until Game 4 of the Heat's second-round series against the Boston Celtics – and he played less than three minutes that night, picking up two fouls in the process. After he played just four minutes in the opener of the Eastern Conference finals, it seemed unlikely that Haslem would be able to contribute much for the remainder of these playoffs.

"It's hard to explain U.D. and what's inside of him – the championship heart," Heat coach Erik Spoelstra said. "None of us really anticipated he would be available to this extent."

Bosh and center Joel Anthony are the starting post players for the Heat. But when it came to guarding Nowitzki in Game 1, Haslem did most of the heavy lifting.