The Boston Celtics may have earned the No. 1 seed in the Eastern Conference playoffs by going 53-29 during the regular season, but that doesn't mean they've won over all their critics.

In fact, they haven't even completely won over their own owner, Wyc Grousbeck, who has some cause for concern as the postseason gets underway this weekend.

Grousbeck thinks it's important that the Celtics continue to improve even though the regular season is over. If the team is content with the No. 1 seed, he foresees an early playoff exit.

According to WEEI.com, Grousbeck believes the Cleveland Cavaliers are still the team to beat in the Eastern Conference:

“I don’t think we’re as good as Cleveland,” Grousbeck said. “If we got a chance to play them in the postseason, I’d love to see it, but I’m not sure how it would turn out.”

Perhaps Grousbeck should have said that any team with LeBron James should be considered the favorite to win the Eastern Conference, as James has appeared in six-straight NBA Finals as a member of the Cavs and the Miami Heat.

Grousbeck did pay a compliment to the Cleveland superstar, though, crediting him for guiding the Cavaliers to a recent 114-91 victory over the Celtics in Boston:

"That was Cleveland clicking on one cylinder, if you ask me,” he said. “I don’t want to disrespect them, but I saw LeBron [James] take that game over single-handedly. He had a lot of help, etc. ... I’m not disrespecting Kyrie [Irving] or Kevin Love or anyone else on the team, but LeBron took that over for a period of about six possessions there on the offensive and defensive end of the court. He dominated us. I have to give him a ton of credit. It showed us that we’ve got a ways to go.”

The good news is that, if the Celtics keep advancing, they won't have to meet LeBron and the Cavs until the Eastern Conference Finals. Of course, Boston would be unwise to look past the Chicago Bulls and the winner of the Atlanta Hawks/Toronto Raptors series, but those games could also serve as learning experiences for the mostly young Celtics squad.

If the Celtics and Cavs do meet in the Eastern Conference Finals, a lot of pressure will be placed on Avery Bradley (who will likely be tasked with limiting LeBron) and the Boston defense, which has struggled at times this season.

To win an NBA title, though, you have to beat the best teams. So, if the Celtics want to raise their NBA-record 18th championship banner, taking down LeBron, Irving, Love and the Cavaliers is something they'll likely have to do.