PITTSBURGH -- One takes his nickname from London's lumbering clock tower. The other from Snoopy's smooth alter-ego.

But "Big Ben" Roethlisberger and "Joe Cool" Flacco have both stood tall over the competition and remained poised during the playoffs.

When the two quarterbacks meet in the AFC Championship between the Baltimore Ravens and Pittsburgh Steelers at Heinz Field on Sunday, one may see a younger version of himself, the other a look at what he may one day become.

When Roethlisberger made his NFL debut as against the Baltimore Ravens on Sept. 19, 2004, it was meant with mixed reactions from the locker room.

Current New York Jets offensive guard and former Steeler Alan Faneca was less than thrilled about the rookie Roethlisberger taking over for an injured Tommy Maddox.

Roethlisberger entered the game in the third quarter, throwing for 176 yards, two touchdowns and two interceptions.

The Steelers would lose the game 30-13, but that would be the last game they'd lose all season.

Roethlisberger would lead the team to a 15-1 regular season record while breaking rookie quarterback records for completion percentage (66.4) and passer rating (98.1) held by Pittsburgh native and Miami Dolphins Hall of Fame quarterback Dan Marino.

The Steelers would fall short of the Super Bowl, losing to the New England Patriots 41-27 in the AFC Championship at Heinz Field.

This season, Flacco found himself thrust into action due to a season-ending injury to quarterback Kyle Boller.

Teammates were vocal about their wishes for former Heisman Trophy winner Troy Smith to start, but first-year coach John Harbaugh stuck with rookie Flacco.

Flacco won his first two games before a three-game losing streak that included a 23-20 overtime loss to the Steelers in week 3.

Flacco would guide the Ravens to a 11-5 record and wild card birth in the playoffs, but couldn't get past the Steelers a second time, losing 13-9 at home in week 15.

Flacco finished the regular season with an 80.3 quarterback rating, throwing for 2,971 yards, 14 touchdowns and 12 interceptions in 16 games.

"He's no longer a rookie," said Tomlin of Flacco while speaking at his weekly press conference Tuesday. "This guy has the hardware that says otherwise. He's led a football team. He's obviously gained the respect of a very veteran football team."

Roethlisberger threw for 2,621 yards, 17 touchdowns and 11 interceptions for a quarterback rating of 98.1 rating in 14 games during his rookie campaign.

Flacco became the first rookie quarterback to win two playoff games when the Ravens defeated the Miami Dolphins 27-9 in the wild card round and Tennessee Titans 13-10 in the divisional round.

"I knew about him when we were up on them the first time we played those guys and he took them down the field and forced overtime. I saw enough at that point to know that we're going to have our hands full with this guy for a very long time," said Tomlin.

At age 23 in his second season, Roethlisberger became the youngest quarterback to start and win a Super Bowl.

A win Sunday would give "Joe Cool" a chance to upstage his predecessor. A loss would place him in "Big Ben's" shoes from 2004 -- one win short of making it to the big stage.