SEATTLE — Sean Locklear didn’t have anyone to block. Shaun Alexander’s eyes got as big as the gap in the Cincinnati defense. And as for center Chris Spencer, he just wanted to get to the line of scrimmage and do his job as quickly as possible.

“I was like: oh, man,” Spencer recalled, “snap it fast before they get somebody in there.”

On what would amount to the biggest play of Sunday’s game against Cincinnati — and possibly the most important play of the season to date — the Seattle Seahawks took advantage of a hole in the Bengals defense to get a key first down and, in the process, set up the game-winning touchdown pass.

“As an offensive lineman, you always want to get those,” Spencer said after a fourth-down conversion during the final two minutes of Sunday’s 24-21 win over Cincinnati. “It sends a message throughout the league that, if it’s third-and-1 or fourth-and-1, we’re going to get that. It gives you the confidence to get it the next time.”

For the second week in a row, the Seahawks turned a fourth-and-short into a big gain. Last week against Arizona, Shaun Alexander scored a 16-yard touchdown on fourth-and-1. On Sunday, he converted the fourth down with a 14-yard run to the right. At the time, Seattle was trailing by four points with less than two minutes to go. One play later, Nate Burleson caught a 22-yard touchdown pass for the game-winning score.

Alexander’s run may have been the most important play of the game, in that it kept Seattle’s hopes alive. Had he been stopped, the Bengals may have been able to run out the clock and get out of town with a 21-17 win.

But Cincinnati’s defense left too many gaps to stop the Seahawks’ fourth-down play.

One linebacker was stacked up on the left side of Seattle’s offensive line, while the middle linebacker was lined up in the gap over the top of right guard Chris Gray. That left a huge gap on the right side, which is just where the Seahawks had been planning to run.

“I think they misaligned,” said Locklear, Seattle’s right tackle. “I thought they were going to bring somebody over there (on the right side), so I’m looking and waiting, and they never brought anybody over there.”

And so Locklear, an offensive lineman by trade, was left in the unfamiliar position of having nothing to do. The only obstacle in front of him was a Bengals linebacker who was already being handled by fullback Mack Strong. Locklear just threw himself into the collision for lack of anyone else to hit.

“You wouldn’t expect that on fourth-and-1, with the ball game on the line, but they misaligned,” Locklear said. “Whatever happened, they misaligned and we took advantage of it.”

The conversion also served as retribution for Alexander, whose final play in the previous week’s game saw him misread an audible and botch what was supposed to be a handoff from Matt Hasselbeck.

Whether that play was a factor or not is subject to debate, but for whatever reason the Seahawks did not use Alexander in any of their first four short-yardage plays of Sunday’s game against Cincinnati. Three times on third-and-3 or shorter, the Seahawks called pass plays. The only other short-yardage situation, on third-and-1, saw Seattle ran a quarterback dive.

So when the Seahawks had a fourth-and-1 at the Cincinnati 36-yard line, with 1:41 left on the clock, it was no sure thing that Alexander would be the one to get the ball.

But he did, and he made the play of the day.

“The boys blocked it very well,” Alexander said. “Sean Locklear rolled the whole thing down. I said, all right, Mack, I’m just going behind you.”

Coach Mike Holmgren said that the fourth-down call was not the same one as he had drawn up for the previous week’s play that resulted in a fumble. That was also a running play to the right side, but it never got off the ground.

“I thought it was a good call last week,” Holmgren said. “We just didn’t do it very well. (Against Cincinnati on Sunday), they executed. Cincinnati kind of bunched in there to stop something right up the gut, and we popped it outside. And sometimes that works for you.”

While the Seahawks were just 2-of-8 on fourth-down conversions in 2006, they’ve been a perfect 2-for-2 this year.

“We haven’t had the kind of success in (short-yardage situations) that we would like,” tight end Marcus Pollard said. “When you get one, then get a big run on top of it, that’s always a confident builder — for the offensive line, for Shaun and for everyone playing.

“I’d like to say we could be 100 percent on fourth-and-1. But we still have to make plays and make it happen.”