The Detroit Lions have a frustrating postseason history. They have made the playoffs only 11 times since they were last N.F.L. champions, in 1957. In 10 of those appearances, they lost in the first round. Their only playoff win in more than half a century was a divisional-round win over the Dallas Cowboys in the 1991 season, back when Wayne Fontes was still their coach.

But this year, the Lions are 7-4 and lead the N.F.C. North by a game. The New York Times’s Upshot simulator estimates they have a 70 percent chance of making the playoffs. It is an impressive performance for a team that was 7-9 last season and was expected to be among the N.F.L.’s also-rans this year.

So is this the year for playoff glory? Unfortunately, probably not. The Lions’ success has largely been built on sand. Here are eight reasons the Lions will not be winning that elusive playoff game this season, either.

1. They Never Win Big

The Lions, unlike most good teams, never win decisively. Every victory this season has been by 7 or fewer points. A bounce here or there, and their record might well be a lot worse. Take a look at all the successful teams over the years: Although they may win a few nail-biters, they will always have a good smattering of blowout wins, too.