The Lions offense can't survive without Calvin Johnson
The Lions showed in Week 3 that they can get by without Reggie Bush. In Week 5, they showed that they can't get by without Johnson. There is enough talent behind Bush at running back to make up for his absence, but the drop off at wide receiver from Johnson to everybody else is enormous. Nobody at wide receiver gave the Packers anything to be concerned about, allowing them to put their focus on shutting down Bush. The net result: Only 286 total yards and 9 points. This offense is nothing without Megatron.
Sunday was a big step back for the offensive line
On a somewhat related note, the offensive line was terrible on Sunday. Matthew Stafford was sacked 5 times, and Lions running backs rushed for only 65 yards on 18 carries (3.6 yards per attempt). This was partially a product of Johnson being out, as the Packers had the luxury of loading up the box without having to worry about getting beat deep. What's more, some of those sacks were because nobody could get open downfield, so not all of the blame goes to the O-line. Even so, the Packers were routinely blowing up plays, and the O-line has to be better no matter who is out at wide receiver.
DeAndre Levy is having a career season
It wasn't all bad for the Lions on Sunday. Case in point: Levy's fine season continued in a big way. He has been excellent for the Lions, and he led the team on Sunday with 14 tackles and 3 tackles for a loss. He once again blew up a screen with a perfect read, and he also had a pass defense by batting the ball down on a third-and-short play. Levy has been a real nice surprise so far this season for the Lions defense.