By Simon Evans

MIAMI | Fri Nov 16, 2012 9:51am EST

(Reuters) - The league's finest young quarterback takes on one of the masters of the trade when rookie Andrew Luck and the Indianapolis Colts face Tom Brady and the Patriots in New England on Sunday.

Luck came into the league this year as the number one draft pick and with a stellar reputation from his college career at Stanford.

His coming to a young Colts team going through a major rebuilding, with a new coaching staff and following the departure of his predecessor Peyton Manning, meant high hopes were tempered with calls for patience in his first season.

But the Colts head into Sunday's game with the same 6-3 record as the Patriots and with their young quarterback having already thrown for 2,631 yards and 10 touchdowns as part of a totally reworked offense.

His success has not surprised many.

"I thought that he would come in and do well, it is the rest of the rookies on offense that have exceeded my expectations," said Colts offensive coordinator and interim head coach Bruce Arians.

"When we played the Dolphins, on the game-winning drive, we have eight first-year players out there."

Brady didn't start a game in his first year, back in 2000, and says he is full of admiration for rookies like Luck who are able to learn so quickly the demands of the pro game.

"It's always challenging for those rookies. As a rookie I was like fourth-string and eating nachos before the game in the stands. There wasn't much of me thinking of playing so I always admire those rookies who can do it," he said.

Patriots head coach Bill Belichick has been impressed with Luck's ability to improve quickly through his first year.

"It looks like he is getting better and better every week, playing with more and more confidence. He's got a great core of receivers to throw it to," he said.

"He shows a lot of poise to make all those throws and is very athletic in the pocket, he can scramble to run and can buy more time in the pocket to throw the ball down the field.

"He's playing like a very experienced and poised player."

The Pittsburgh Steelers' ambitions have taken a blow with the loss of quarterback Ben Roethlisberger to shoulder and rib injuries.

The Steelers will have to rely on veteran back-up Byron Leftwich who hasn't started an NFL game since the 2009 season against the Baltimore Ravens this week.

The Ravens lead the AFC North on 7-2 while the Steelers are on 6-3.

Injury losses are also likely to impact Monday night's game in San Francisco between the 49ers (6-2-1) and the Chicago Bears (7-2).

Both Bears quarterback Jay Cutler and his 49ers counterpart Alex Smith suffered concussions last week and are at risk of missing the NFC clash with Jason Campbell the deputy for the Bears and Colin Kaepernick Smith's substitute.

The Atlanta Falcons (8-1) look to bounce back from their first loss off the season when they host the Arizona Cardinals.

(Editing by Gene Cherry)