DETROIT — It's easy to blame the loss on Ryan Mathews and his fumble with 2½ minutes left.
And it's easy to blame the loss on Carson Wentz's ill-advised bomb to Nelson Agholor that was intercepted when the Eagles were only 40 yards from game-winning field goal range.
And those two turnovers — the Eagles' first turnovers this year — were certainly costly plays Sunday in the Eagles' 24-23 loss to the Lions.
Bottom line, though, is that the Eagles' defense wasn't ready to play.
The Lions opened the game with touchdown drives of 75, 80 and 75 yards, and although the Eagles' defense played exceptionally well after halftime, the damage had been done.
And when assessing blame, Jim Schwartz's group deserves a big share.
"We just can't spot anybody 21 points in the first half," defensive end Brandon Graham said. "We just can't let that first half happen like that. We just can't do that.
"That was a big part of the game. We played better in the second half but then they made the plays at the end of the game to win it."
The Eagles have been brilliant in the second half all year. They haven't allowed a second-half touchdown on defense since Pat Shurmur was head coach, and they've allowed a total of just six second-half points on defense.
But when you dig a 21-point hole, you leave yourself very little margin for error.
The Eagles are 1-19 in their last 20 games in which they've allowed 21 first-half points, and the only win was the DeSean Jackson punt return game at the Meadowlands in 2010.
"We look back at the first half and realize that, both sides of the ball, we kind of shot ourselves in the foot," safety Malcolm Jenkins said. "I'm sure there were a lot of bad things we'll see on tape that you can't do. Losing contain. Misfitting gaps. All those things we can correct."
Eagles defensive coordinator — and former Lions head coach — Jim Schwartz did some surprising things in the first half, playing a lot of Mychal Kendricks and Stephen Tulloch, which left the Eagles' two best linebackers — Nigel Bradham and Jordan Hicks — on the bench.
It didn't work.
The Lions racked up 199 yards and 17 first downs before halftime, and Matthew Stafford capped all three Detroit drives with touchdown passes.
"They weren't running anything mind-blowing or Earth-shattering," Jenkins said. "They had a couple wrinkles we hadn't seen."
In the second half, everything changed.
Bradham and Hicks were back on the field, and the running gaps and passing lanes that were wide open for the Lions in the first half evaporated.
The Lions netted just 19 yards on their first four second-half drives, which is why Mathews' fumble hurt so much. If the Eagles had just punted down inside the 20, it seemed impossible for the Lions to be able to drive the length of the field to get into field goal range.
But Mathews' fumble — at the Eagles' 45-yard-line — gave the Lions good enough field position that one big play — Stafford's 27-yard completion to Golden Tate on a 3rd-and-4 — got them in field goal range.
The Lions had only 18 second-half yards outside that one play.
"We saw what happens when you do your job snap-in and snap-out," Jenkins said. "Eleven guys playing hard, playing together and communicating. You see the results of that.
"We made some schematic adjustments, but it really came down to we're going to man these guys up, everybody win their matchup and do their job and guys did it. We played and we communicated."
The Lions had 199 yards in the first half, 45 in the second. They were 17-for-77 rushing before halftime, 10-for-3 in the second. They went from 122 net passing yards before halftime to 42 after.
"We made some adjustments and it was obvious what they were trying to do in the first half," Connor Barwin said. "They got on us. The second half they tried to do the same stuff, we just played it better across the board."
The Eagles are allowing an average of 166 yards in the first half and 101 in the second half. The defense is giving up an average of 9½ points in the first half and 1½ points in the second half.
They have yet to allow more than 86 net passing yards in the second half of any game.
"Felt like Detroit in the first half was maybe a half-step ahead of us a little bit and then in the second half we got together and [the defense] did an outstanding job," head coach Doug Pederson said. "They gave us obviously an opportunity to win the game."
A performance like Sunday's is rare.
This was only the 17th time in franchise history the Eagles have allowed 21 or more points in a first half and three or fewer in a second half.
They're 5-12 in those games. Which just goes to show you that you really do need two quality halves to win a game.
"We're 3-1, it's a long season, and for us we've just got to get back on the path that we started," Graham said. "Hey, just happy it happened early in the year so we can make the corrections and get it right."
Bottom line is despite an ugly first half in Detroit, the Eagles' defense is still No. 1 in the NFL in scoring defense, allowing just 11 points per game.
They're No. 6 in pass defense, No. 4 in first downs allowed, No. 2 in yards allowed per game, No. 3 on third down and No. 3 in rush defense.
The Eagles, 3-1, face the 3-2 Redskins on Sunday at FedEx Field in Landover, Md. The Skins have won three straight.
"We're comfortable and confident with where we are right now," Jenkins said. "Now it's on to next week."