First applied to the Audi A3, and more recently on its A1 Sportback concept seen at the 2008 Paris show, the Four Ring brand’s latest Sportback-inspired intrepretation — the Audi Sportback Concept unveiled at the 2009 Detroit show — is by far the most luxurious and daring of its five-door efforts to date and no doubt serves as a thinly-veiled concept version of the soon-to-arrive Audi A7.

While the Sportback Concept is at first glance yet another take on the now painfully cliche “four-door coupe,” it’s the addition of hatch that sets it apart from the CLS-Classes of the world. At 16.24 ft long, 6.33 ft wide and just 4.59 ft high, the Sportback certainly sports coupe-like dimensions. The Sportback’s roofline and frameless doors make for a silhouette that appears to flow seemlessly from front to back, and the wheel wheels wash over the concept-size 21-inch rims. Audi says the design has a dramatically reduced number of lines, and we can’t argue with that.

Audi’s now famous LED units for the Sportback are wider and flatter than past efforts, and the side mirrors are reportedly styled after jet wings for what the brand calls a “winglet” look. Other design cues include a new take on Audi grille that’s not as high and loses the vertical struts, and air intakes under the headlights that help accuentate the Sportback’s low and wide stance. Out back, there’s plenty of A5 in the design, along with four exhaust pipes and a diffuser that augment the car’s sporting intentions.

A large glass roof opens up the Sportback’s cabin, which was designed with a focus on the driver and features all the usual Audi bells and whisles and heaping helpings of leather and wood trim with aluminum accents. The wide center console extends all the way through to the rear of the car. Four sport seats lend the car a GT feel, and Audi says leg, head and shoulder room will be more than sufficient for all passengers. In addition, at 17.66 cubic feet, the trunk space is impressive for a car like the Sportback.

The Sportback Concept employs the same basic architecture as the new A4/A5, with a couple of notable exceptions. For the first time, Audi has employed its electromechanical steering system in a longintudinal engine vehicle, which consumes less energy when steering and saves a bit on fuel consumption. Stopping the Sportback are a set of ceramic brakes at all four wheels, which Audi claims will last more than 180,000 miles. Up front, the six-piston, ventilated units measure 14.96 in., with 14.02 in. floating caliper units residing behind the massive 21-inch rear wheels.

Audi is a big proponent of diesel power, with the soon-to-arrive Q7 TDI and the just announced A3 2.0 TDI coming to the U.S. It comes as no surprise that the Sportback features the same 3.0L diesel unit that powers the Q7. The engine, which produces 225 horses and a healthy 406 lb-ft of torque, is mated to Audi’s new eight-speed tiptronic automatic transmission. And of course, quattro all-wheel-drive is standard issue equipment.

The Sportback, which tips the scales at just south of two tons (3968 lbs) has a reported drag coefficient of .30, with 0-62 mph coming in slightly less than seven seconds on to a top speed of 152 mph, according to Audi. While not a stunning number, this one is — an MPG rating that Audi says reaches an extremely impressive 36.75 mpg in U.S. measurements. Solid performance, exceptional mileage, Audi style…We like we we’re seeing so far.

While there are several concept cues on the Sportback that won’t make it to production, with its A4/A5 underpinnings, existing powertrain and production-look cabin, the Sportback Concept is a car with the kind of pronounced sportiness we’re definitely looking forward to seeing in production trim.