Nick Foles' Oct. 20 performance against the Dallas Cowboys remains one of the mysteries of the Eagles season. Foles has tried to explain what happened. The coaching staff has tried to examine what happened. Analysts have tried to understand what happened.

But there remains no explanation for why a quarterback who has been so effective throughout much of the season could look so overmatched, which he did when he threw for only 80 yards in three quarters while completing 37.9 percent of his passes before leaving the game with a concussion.

There was no previous injury or any specific cause that could be identified other than a bad day for such a bad day.

"There's just some things in life that if you try to figure it out, it will drive you crazy," Foles said. "It's easy just to say, 'It was a bad day.' If I look into every little meaning and every little thing I did and try to break it down, I'd drive myself crazy."

The game is an aberration over the course of the season. In Foles' seven starts since the Cowboys game, he has averaged 286.6 yards and 2.7 passing touchdowns per game with a 66.7 percent completion percentage. Foles has his second opportunity of the season against the Cowboys on Sunday, when the Eagles visit Arlington, Texas, with a chance to win the NFC East.

The quarterbacks have watched the Oct. 20 Dallas game this week, but not to try to diagnose Foles' problems in that game. The point of watching the Cowboys film was to examine how their defense played against the Eagles.

Foles reviewed the Dallas game upon recovering from the concussion, when he acknowledged that his accuracy was the biggest issues. He also held the ball longer than he ordinarily does.

Foles spent the week after the game focusing on mechanical issues such as his footwork and following through on his passes, although this is not an outlier from most weeks. The second-year quarterback is a stickler about his mechanics. He begins practice with daily footwork drills and has repeatedly explained his emphasis on the direction of his left shoulder when he throws.

Foles recovered from the Cowboys game with a seven-touchdown performance in his next time on the field against the Oakland Raiders, which coach Chip Kelly said is evidence of Foles responding from the bad outing.

"I look at it in a critical manner," Foles said. "I know we've grown as a team since then. And I'm going to use it to try to get better. I'm going to look at where we made mistakes, where could we have capitalized where we didn't."

Kelly expressed on Monday how much the team has grown since Week 7. The players have also mentioned it, specifically referencing Foles. The Cowboys game was his second start of the season and eighth start of his career. So he has nearly doubled the amount of game experience since that afternoon.

Two days after the game, offensive coordinator Pat Shurmur said all the problems against the Cowboys were correctable. He insisted then that it was not a step back in Foles' development, and warned against making more out of it than what it was.

When discussing the game this week, Shurmur identified the problems that day as more than the quarterback play. Running back LeSean McCoy pointed out that he didn't have a good day, either. The message was that as bad Foles as looked that day, he was not the only one.

"We dropped balls, we weren't on the same page at times with who to block," Shurmur said. "We threw the ball inaccurately at times. We didn't do a good job coaching and give them the best opportunity to succeed as players. We just weren't very good. We can't do that this Sunday."

Foles said this week that he will not dwell on that Cowboys game or worry about a pass that he missed in October, because that will do nothing for him in December. His concern is how he is practicing and playing this week, and his recent track record is encouraging.

Foles insisted that one game will not define him. It did not. But one more good game against the Cowboys will make what happened in October a distant memory.

"I've been asked the question several times, and everybody wants an answer," Foles said. "The answer is, 'We had a bad day.' "

Extra points

Offensive lineman Julian Vandervelde missed practice with a back injury, a new injury for the Eagles backup center. . . . Safety Colt Anderson continued to miss practice with a knee injury. Anderson missed last Sunday's game. . . . All other Eagles were full participants in practice, including safety Earl Wolff, who is dealing with a knee injury.