It is rare when history isn't on the side of the Boston Celtics.

But that's the case as they prepare to take on LeBron James' Cleveland Cavaliers starting Sunday. LeBron is a first-round nightmare of an opponent.

LeBron James has averaged 29.5 points, 8.7 rebounds and 6.8 assists in 43 first-round playoff games. AP Photo/Mark J. Terrill

By many measures, James has been the league's most dominant first-round player in the modern era of the playoffs, dating to the expansion to 16 playoff teams in 1984.

James, who has played in every postseason since 2006, has a career postseason record of 36-7 in the first round. That means James, at .837, has a better first-round winning percentage than Michael Jordan (31-15 in the first round), Kobe Bryant (50-24), Shaquille O'Neal (45-23) and Tim Duncan (55-24).

Larry Bird and Magic Johnson played on historic teams loaded with Hall of Famers in the 1980s and '90s. But in the first round at least, James' record has been better. Bird was 22-8 in first-round games with the Celtics and Johnson was 26-6 with the Lakers.

"It's a totally different mindset," James said of entering the playoffs. "There's so many games in the regular season, you can't give all your time to just one opponent because you can have four in five nights. ... But in the postseason, you have at least four times that you're going to see that opponent. At this point, there's not many different sets that you're going to see. You're going to see the same personnel. So I'm able to lock in."

James hasn't lost a first-round playoff game since 2012, leading Miami to sweeps the past two seasons over the Milwaukee Bucks and Charlotte Bobcats.

First-Round Playoffs Career Comparison Name Record PCT PPG LeBron James 36-7 .837 29.5 Magic Johnson 26-6 .813 19.6 Larry Bird 22-8 .733 25.4 Kobe Bryant 50-24 .676 25.2 Michael Jordan 31-15 .674 36.8

Over the past six seasons with the Cavs and Heat, James is 24-3 in the first round. Every year in that span, his team has been either the No. 1 or No. 2 seed, which of course always made his team is the heavy favorite, but he has barely stumbled.

The only times he was on teams that lost two games in the first round were 2006 and 2008, when the Cavs beat the Washington Wizards in six games. Both times, the Cavs were the No. 4 seed and the Wizards No. 5.

In his first-ever playoff game in 2006, James put up a triple-double. He also hit game-winning shots in the final 10 seconds of two games in that series. He hasn't slowed from that early success. In his 43 first-round playoff games, James has averaged 29.5 points, 8.7 rebounds and 6.8 assists while shooting 51 percent according to ESPN Stats & Information.

Jordan averaged 36.8 points, 6.2 rebounds and 5.8 assists in 46 career first-round games. In an era when efficiency wasn't nearly as closely watched, Jordan came out well there too; he averaged 52 percent on 26 shots per game and was a sizzling 85 percent on 11 free throws per game. That includes the 44 points Jordan scored in Game 5 of the 1989 first round, when he hit "The Shot" against the Cavs and finished that game 17-of-32 from the field.

There is little doubt that a big reason for James' first-round strength over the last decade is the relative weakness of the Eastern Conference during that time. Including the Celtics this year, over the last seven playoffs, James' first-round opponents have an average .498 winning percentage.

LeBron James and the Miami Heat swept the Charlotte Hornets in the first round of last year's playoffs. Issac Baldizon/NBAE/Getty Images

(These mostly lopsided series involving one of the game's most marketable players could be offered as part of the case for the league to allow the best 16 teams into the playoffs regardless of conference.)

Naturally, a historic first-round record is hardly a career priority for James. His critics could easily point out the contrast of his Finals record, which stands at 11-16 with three overall defeats against two titles, to his peers. Jordan, Johnson, Bird, Bryant, O'Neal and many Hall of Famers have him on this account. James would be the first to point out that titles are what matter most.

But this week is the start of another first round, which James must deal with before he can even think about improving that Finals mark. And it also means the Celtics are probably in trouble.

"We have our own expectations," James said. "We don't worry what everyone else thinks of what we should do. It's about what we expect out of ourselves.

"We had a pretty, pretty good regular season. I wouldn't say great. I'm not satisfied. I'm never satisfied."

ESPN.com reporter Dave McMenamin contributed to this story.