Last season, the Detroit Pistons’ title run caught a lot of observers by surprise. They entered with a solid but unspectacular 54-28 record and, at a glance, appeared no better than the second-best team in the profoundly weaker Eastern Conference. What that casual glance missed was that Detroit had gone 20-4 after All-Star forward Rasheed Wallace joined the team. The expectations for a team entering the postseason on a .833 roll are different from one that has played .659 ball all season.

Several of this spring’s playoff contenders have had split seasons. Whether it’s due to coaching changes in Denver and Memphis, personnel changes in Boston and New Jersey, or tactical changes in Chicago, each of these teams enter the postseason with a record that masks its true strengths. With that in mind, it’s worth asking who could pull off a first-round upset.

George Karl’s Denver Nuggets are not the same team that struggled to a 17-25 (.404) record during the first half of the season under coaches Jeff Bzdelic and Michael Cooper. They’ve gone 29-6 (.829) since Karl took over on January 28, establishing themselves as a legitimate threat in the bottom half of the Western Conference bracket.

The most obvious change is on offense. Under Cooper in January, the Nuggets averaged 95.4 points per game and shot 44.6% from the field including an abysmal 23.5% from behind the arc. Karl then implemented a system that stresses spreading the floor by shooting more 3-pointers, and after a brief period of adjustment, the Nuggets exploded. In March, Denver averaged 109 points per game on 49.3% shooting from the field and a sizzling 42.9% from behind the arc.

At present, the Nuggets sit in the seventh slot in the West, but they are only a half game behind Houston for the sixth seed. If they finish seventh, they will clash with San Antonio in a classic battle of styles that the Nuggets are unlikely to win. But if they pass the Rockets, they will be in very good position to upset Seattle, a team that has limped to the flag, losing its last five games.

Like the Nuggets, the Memphis Grizzlies have been a different team since making a coaching change, but their major improvement has come at the defensive end. The Grizzlies were 5-11 (.313), and coming off a 90-82 loss to the Knicks at the Garden when Mike Fratello took over on December 2. Under the Czar’s rule, they’ve gone 39-22 (.639) while playing some tenacious defense. After playing the first month of the season under Hubie Brown and Lionel Hollins, the Grizzlies were allowing 95.4 points per game; Fratello has them yielding only 89.2 points per game.

The perception is that the Grizzlies have slipped lately, but it’s more a matter of their going 70 mph on the highway and getting left in the dust by Denver’s 90 mph. The Griz will almost certainly finish in the eighth seed and make a very intriguing great defense vs. great offense matchup for Phoenix in the first round. The two teams split their four games this season, each winning one on the other’s home court.

In the Eastern Conference, the most impressive late-season surge has occurred in Boston. The Celtics were 27-28 before reacquiring power forward Antoine Walker at the trade deadline; they’ve gone 15-7 (.681) since. A closer look, however, reveals that their offensive and defensive numbers are strikingly similar for the month before and after Antoine. Without concrete statistical improvement, it seems that the Celtic’s hot streak owes as much to an easy stretch of schedule that featured several games against the weak sisters of the East – Charlotte, Atlanta, and Toronto.

Barring a total collapse, the Celtics will enter the playoffs as the no. 3 seed, but they will be a potential upset victim of the likely no. 6 seed, either Washington or Indiana. Both the Wizards and Pacers are likely to finish with a better record, but observers may be fooled by the Celtics’ post-Walker run.

By now, any local fan must be wondering about the Nets with Vince Carter. Indeed, Vinsanity’s arrival, along with Jason Kidd’s return to good health, has transformed the Nets, despite the loss of Richard Jefferson for the season. Since Kidd resumed starter’s minutes in a December 27 game loss to Detroit, which coincided with Carter’s arrival in the New Jersey lineup, the Nets have gone 29-22 (.569). That may not seem like much, but consider that the team was 9-17 (.346) to that point.

Should the Nets beat Indiana tonight and Philadelphia on Sunday, they will stand an excellent chance of passing the Cleveland Cavaliers, who face three playoff-bound teams in their final five games and are only 6-7 since coach Paul Silas was fired. Still, it’s useful to remember that the Nets are likely vying for the seventh or eighth seed, and the right to be summarily dismissed from the playoffs by the Heat or Pistons.

Chicago has made no in-season personnel or coaching changes, but they have had two distinct campaigns. They started as the same old post-dynasty Bulls, going 1-10 (.091) in their first 11 games. Then they adjusted the lineup to start Eddy Curry at center, move Antonio Davis to power forward, and go with a nine-man rotation featuring reserves Tyson Chandler and Ben Gordon in key fourth-quarter roles.

Since then they’ve gone 43-23 (.652), which may explain why the recent absences of Curry and forward Luol Deng haven’t slowed their surge. Pundits may see a novice playoff team missing one and possibly two starters, and presume that Chicago will be a likely target for a playoff upset, but the Bulls’ depth and defensive intensity suggest otherwise.

As the fourth seed, they will likely face either Indiana or Washington, and should beat either, but they match up poorly against Miami and will be lucky to extend a second-round series to six games.

Almost every NBA post-season features a handful of upsets, and this year should be no exception. Several of the series that look like walkovers will be very competitive, and teams like Denver, Memphis, and Chicago are poised to go farther than their regular season records would indicate.