Sports Illustrated ran an informal poll of nearly 20 NBA executives asking them to rank the top three teams in the league. The vast majority of the participants voted for the Miami Heat to win the 2013 NBA Championship. The article has more insight into the results, as well as specific verbatim quotes for each team in the mix. No votes were cast for other contenders such as the Celtics, Spurs, Bulls, Pacers, Grizzlies, Clippers, etc.

Via Sam Amick | Sports Illustrated
According to a group of basketball minds (including 10 general managers) who were asked to pick their favorites for the 2013 championship, the Celtics and every other team not named the Heat, Lakers or Thunder are second-class citizens in the league's changed landscape.

The final tally, with three of the voters submitting only first-place votes: The defending champions in Miami received 14 first-place votes, one second-place vote and two third-place votes; their Finals foe, Oklahoma City, garnered two first-place votes, five second-place votes and eight third-place votes; and the Lakers, who have added Dwight Howard and Steve Nash to Kobe Bryant and Pau Gasol, got two first-place votes, nine second-place votes and five third-place votes.