SEATTLE - Poise continues to be rookie quarterback Dak Prescott's most impressive attribute.

Prescott, who was near perfect in his first two preseason games, passed another test Thursday night.

Tony Romo went down three plays into the game with back problems. Suddenly, Prescott - who wasn't supposed to play until the third quarter - was forced into action.

Prescott didn't blink against one of the league's top defenses. On his first play, he converted a third-and-8 play into a first down with a 12-yard pass to Cole Beasley.

On the Cowboys' ensuing possession, Prescott led the Cowboys on a seven-play, 81-yard drive that he finished off with a 17-yard touchdown pass to Jason Witten to give Dallas a 7-0 lead.

Witten was locked in tight man-to-man coverage against Seattle linebacker K.J. Wright. But with Wright's back to Prescott, he unleashed the pass and gave Witten a chance to make a play. Witten rewarded Prescott by making the catch over the top of Wright for the score.

"He comes in and shows great poise," Witten said at halftime about Prescott. "He trusts his players and he trusts the system. The situation and circumstances are not too big for him."

Prescott turned in a perfect passer rating last week against Miami. He wasn't perfect against the Seahawks, but he certainly didn't look like a rookie either.

He again showed his poise under pressure late in the second quarter when he executed the hurry-up offense.

The Cowboys took possession with 3:17 left before halftime. Prescott led Dallas on a 12-play, 54-yard drive. He completed a second-and-15 pass for an 11-yard gain to Alfred Morris in the final seconds. Prescott rushed to the line of scrimmage to spike the football with :03 seconds left, giving Dan Bailey the chance to make a 40-yard field goal as time expired to tie the game at 10.

Prescott played into the third quarter. He wasn't replaced by Jameill Showers until the final 27 seconds of the third.

Prescott finished 17-for-23 passing for 116 yards and the touchdown. And at least two of the incomplete passes were drops by Terrance Williams and Devin Street.

Through three preseason games, Prescott is 39-for-50 passing (at least four incompletions are drops) for 454 yards and five touchdowns with no interceptions. He also has two rushing touchdowns.

Prescott has done nothing to give the Cowboys any pause about making him Romo's backup to start the season.

Perhaps receiver Dez Bryant summed up Prescott best while live tweeting the game from back in Dallas:

"DAK is the truth."

DAK is the truth. #DallasCowboys WORLD — Dez Bryant (@DezBryant) August 26, 2016

So far, he has been.

Twitter: @DMN_George.