SEATTLE - Nelson Agholor lost whatever remained of his confidence on Sunday.

His illegal formation penalty didn't exactly lose the game for the Eagles, but it was a momentum shifter, and when the 2016 season is all said and done, it will likely be cited as the mistake that doomed his team's fleeting playoff chances and whatever future the receiver might have had in Philadelphia.

"I've got to get out of my own head," said the Eagles wide receiver, who dropped a pass just a few plays after his penalty. "Pressing so much and worried about so much things."

One moment Zach Ertz was celebrating a 57-yard touchdown that would have tied the score, the next he turned around a saw a yellow flag on the turf.

"Obviously," Ertz said, "I was a little frustrated."

Twelve inches. If Agholor had lined up about 12 inches closer to the line of scrimmage, who knows what would have happened at CenturyLink Field? Instead, the Seahawks kicked a field goal on the ensuing possession and scored the next 13 points in what would be an eventual 26-15 victory.

"I'm not going to say that lost the game, because there was so many other plays," Ertz said of the penalty. "But it was a big part of the game."

It was third down and 6 with 5 minutes, 57 seconds left in the second quarter. The Eagles trailed, 13-7. Agholor lined up left of quarterback Carson Wentz, a step ahead of receivers Jordan Matthews and Dorial Green-Beckham. But he was at least a foot off the ball.

"I thought I covered the line as well as I should have," Agholor said. "But I should have checked with the [official]. That's the No. 1 thing - you've always got to check with the ref, and usually that's one of the first things I do."

It doesn't get any more elementary in football than knowing how to line up properly before the snap. Eagles coach Doug Pederson said he saw that Agholor was short of the line. He said he saw the official motioning for the receiver to move up. He said he thought about calling a timeout.

"I didn't want to necessarily burn the timeout . . . in that situation," Pederson said. "It's just unfortunate."

Wentz, from his vantage point, said that he "didn't notice anything."

"It's a little bit of [Agholor], it's a little bit of the quarterback, a little bit of me," Pederson said, when asked to assign blame. "I've got to make sure everyone understands situational football and formations and the type of things that we do. We just have to coach that better."

When Agholor jogged to the sideline afterward, receivers coach Greg Lewis approached him with the look of a disappointed parent. It was impossible to read his lips, but it's safe to assume that he said something in the vein of: "How many times have we practiced this? How many times have we told you to check with the line judge?"

But the blunders keep happening.

"I don't have the answer for why mistakes happen," Lewis said. "They just happen. It's part of football."

It wasn't the first time that Agholor's failure to line up brought back an Ertz touchdown. Last season against the Redskins, he had an illegal formation penalty that nullified a would-be 11-yard touchdown by the tight end.

"I'm not mad at him at all," Ertz said. "It's not my job to critique how he plays. . . . He's trying his best. It's not like he went out there before the play and said, 'I'm going to take a touchdown away.' "

But he did take a touchdown away. In fact, he's taken away as many touchdowns in his career and he has caught. He pulled in a meaningless two-point conversion late in the game, but otherwise Agholor finished without a catch. It was the first time he was shut out all season.

On the series after Agholor's penalty, Wentz went to the receiver on first down. He found him streaking across the middle wide open. The pass was perfect. The ball hit Agholor in his hands, bounced off and fell to the carpet.

"I've got to go out there and catch the ball like this instead of with my hands because I'm thinking too much and so worried," Agholor said. "That's just a selfish thing I need to stop."

The receiver grabbed the back of his helmet and threw those hands down in frustration after the drop. Agholor has a case of the yips, which are often as much mental as they are physical. Afterward, cameras caught Jordan Matthews addressing his teammate and Agholor just sat there with a blank stare.

The 23-year-old receiver, whom the Eagles drafted in the first round last year, admitted that the pressure was getting to him. He has dropped at least five passes this season.

"I don't like see him down like that," Matthews said. "One good thing - hey, he's being honest and you can't fault him for that. But now that he said it, it's out, so, all right, let's reel it in, let's get back to basics."

Agholor will be the No. 1 target for fan ire, but the rest of the Eagles receivers weren't anything special, either. Early in the fourth quarter, Seahawks quarterback Russell Wilson, who caught a 15-yard touchdown pass from receiver Doug Baldwin on a trick play, had as many yards as the Eagles receivers combined.

Wentz, who wasn't sharp for much of the game, either, said that he still had confidence in Agohlor and the group.

"I see what they can do. I know they can get open," Wentz said. "I know they can make plays. Drops happen. Mistakes happen."

Agholor works as hard as anybody on the team. He routinely stays after practice and catches balls from the JUGs machine. Everyone affiliated with the Eagles insists that he has talent. But it might be time to cut bait.

"Football's a tough game, for tough people," Agholor said. "No matter who I play for or where I'm at, I need to focus on understanding that it's tough. I'm meant for this."

It was hard to believe him.

@Jeff_McLane