They've never competed in a NASCAR Nextel Cup race and won't at Bristol, but three drivers could have an impact on what happens in the series' first Car of Tomorrow race Sunday.

Landon Cassill, 17, graduated last month from a Cedar Rapids, Iowa, high school and is a development driver for Hendrick Motorsports.

Billy Wease, 20, finished second in his ARCA debut last summer but hasn't raced a stock-car since for Penske Racing.

Kevin Hamlin, 28, has started 15 Busch races but none for his current team, Chip Ganassi Racing with Felix Sabates.

Each development driver played a key role in helping their team promote the Car of Tomorrow, which debuts at Bristol Motor Speedway. They tested the cars when their more famous Cup teammates couldn't. They ran mile after mile as crews tried to understand the car. Sometimes, the changes worked. Sometimes, they didn't.

"We sent him to do the dirty work," Kurt Busch said of Wease. "We wanted him to run the tires off the car. It was a lot of monotonous work of just lap after lap, session after session. When we jumped in the car, Ryan [Newman] and myself, we were further down the road."

How could someone with limited stock-car experience provide any valuable information?

"A stock car on an asphalt track is going to have the same feel and the same drive as any other type of stock car," Cassill said. "Loose is still going to be loose, and tight is still going to be tight."

The task for each driver often was the same. The crews had a list of changes -- from shocks and springs to adjusting the front splitter and so on -- to make and then the driver told them how it made the car handle. Sometimes the driver ran two laps. Sometimes it was five laps. Sometimes it was 20 or more laps at tracks such as Greenville-Pickens in Greenville, S.C., Kentucky Speedway in Sparta, Ky., or Iowa Speedway in Newton, Iowa. When the day ended, they had often driven more than 400 miles.

Cassill tested alone at Greenville-Pickens in the offseason and then tested with Jeff Gordon, Casey Mears and Kyle Busch at USA International Speedway in Lakeland, Fla.

"It was important for Jeff and I to tell Steve what the car was doing and being accurate about, especially with a car they haven't used before," Cassill said, referring Gordon's crew chief, Steve Letarte. "It's important to have accurate feedback from the driver. [The crew] can read the data and assume something, but if they read the data and assume something and not hear anything from the driver, then they're really only going to be 60 percent sure what the car is doing."

As each of these development drivers ran laps, they also gained experience. That's important for each. Cassill is young, Hamlin honing his skill and Wease has an open-wheel background.

"Testing is a big help for a development driver because if they were to throw me out there way early with no experience," Wease said, "I'm not going to do as good as I would if they would spend more time with me and take their time and work me up to where they want me to be."