It’s unusual for teams with high expectations to hire untested head coaches. But it’s now happened twice in recent days, as the Chicago Bulls have named Vinny Del Negro to their long-vacant coaching position, and the Detroit Pistons promoted assistant coach Michael Curry to the top job on their bench.

Although both Curry and Del Negro had long careers as role players in the NBA, the situations that led to their hiring couldn’t have been more different. Del Negro was hired after what seemed like one of the most extensive coaching searches in NBA history. The Bulls interviewed two dozen candidates before seemingly finding their man in Doug Collins, the TNT commentator who had coached previously with the Bulls in the late 1980s, as well as with Detroit and Washington.

But Collins withdrew citing an unwillingness to spoil his friendship with Bulls owner Jerry Reinsdorf. (Most people who have watched sports for more than two weeks figured that excuse really meant that the two sides were irreconcilable on money in the contract negotiations.) After Collins withdrew, the team president of the Bulls, John Paxson, conducted second interviews with an assistant coach for Sacramento, Chuck Person, and former Minnesota Timberwolves coach Dwane Casey before selecting Del Negro. By contrast, when the Pistons fired Flip Saunders last week, Curry was announced as the heir apparent.

The Spurs organization has been a hotbed of executive talent in recent years: Del Negro played shooting guard for several NBA teams, most notably the mid- and late-1990s San Antonio Spurs. (He also worked in the Phoenix front office for two seasons before going to Chicago.) His backcourt mate Avery Johnson just finished a four-year run as head coach in Dallas, and Person was a starting forward on those units. The general manager of Seattle, Sam Presti, and the team president of Portland, Kevin Pritchard, are San Antonio alums.

Del Negro’s work with Phoenix reflects well because, like the Phoenix Suns teams of recent vintage, the Bulls are an undersize team that plays its best at a fast tempo. And like the Spurs, the Bulls’ biggest strength is their defense. Both the Spurs and the Suns were orderly and disciplined in their approach to the game — and that’s the first challenge for Del Negro in the Windy City.

Last season, the Bulls entered the campaign with reasonable thoughts toward winning the Eastern Conference Finals. Instead they face-planted, going from 49 wins in 2006-07 to 49 losses last season. Players sulked, bickered, and fought with each other and the coaching staff. Longtime coach Scott Skiles was fired on Christmas Eve, and interim coach Jim Boylan was let go after the season. The Bulls won the lottery and will likely draft University of Memphis point guard Derrick Rose. Del Negro and Rose will be expected to put the Bulls back on track to go deep in the playoffs.

Del Negro will have to sort out a roster filled with young and occasionally redundant talent. His most important task will be integrating Rose into a backcourt that is already a player or two beyond capacity. Kirk Hinrich, Larry Hughes, Chris Duhon, Ben Gordon, and Thabo Sefolosha all played major minutes last season. Hinrich and Hughes, the most experienced guards, are also the most expendable, as their shooting percentages are in decline. The new coach was a career 47.5% shooter from the field, and hopefully he understands the value of that kind of marksmanship.

The frontcourt looks set. Luol Deng and Andres Nocioni fill the small forward spot; Tyrus Thomas and Drew Gooden share power forward duties, and Joakim Noah and Aaron Gray work the pivot. But no matter who plays, Del Negro’s major task will be to restore the Chicago defense. The Bulls led the league in Defensive Efficiency two seasons ago, but they fell to 14th in 2007-08.

Hiring Curry, who had a 12-season NBA career as a reserve swingman and played half of it in Detroit, is probably the first of several moves to be made by the team president of the Pistons, Joe Dumars. When he fired Saunders — whose teams had suffered three straight six-game losses in the Eastern Conference Finals — Dumars cited a lack of urgency among the players. Hiring the coach’s right-hand man seems more in line with maintaining continuity than shaking things up — but rumors are afoot that the Pistons are dangling Chauncey Billups as trade bait in an attempt to bring Denver Nuggets All-Star forward Carmelo Anthony to the Motor City.

If that fails and the Pistons remain in tact, Curry will have one of the more enviable jobs in terms of agenda. In Billups, guard Richard Hamilton, center Antonio McDyess, power forward Rasheed Wallace, and shooting forward Tayshaun Prince, the Pistons have one of the best starting lineups in the NBA. All except Prince are in the late stages of their prime years — but the Pistons also have four youngsters ready to go. Guard Rodney Stuckey and forward Jason Maxiell are already receiving key minutes, and forward Amir Johnson and guard Aaron Aflallo are ready for prime time.

Although both new coaches face strikingly different tasks, both Del Negro and Curry have one thing in common — impatient fan bases. Pistons fans are tired of getting so close to the finals but falling short, while Bulls fans are convinced that their current roster of youngsters are only a few steps shy of joining the Eastern Conference elite. Both men will have to hit the ground running, or their first tenures as head coaches will be short ones.

mjohnson@nysun.com