As Ryan quoted in the links this morning, five No. 8 seeds in the history of the NBA playoffs have taken down a No. 1. (Here's a full list. I had it wrong in the original post.)
Kevin Pelton at ESPN thinks the Pistons have the third highest probability of all the first round series. Pelton looked at "the historical odds of winning a playoff series based on the two teams' point differential during the regular season along with the results of the head-to-head season series" and here is the relevant write up on the Pistons:
The Pistons' chances are inflated slightly by winning the regular-season finale between the two teams, who both rested their starters. Detroit outlasting a 36-point effort from Jordan McRae doesn't really tell us much about what the playoff series will look like.
Nonetheless, the Pistons won a pair of more competitive games against the Cavaliers, including a 96-88 victory in the only game with midseason addition Tobias Harris in the lineup.
Harris, Marcus Morris and Stanley Johnson give Detroit a variety of athletic forwards with enough size to defend LeBron James, who went 5-of-18 with six turnovers in the February matchup. Cleveland is still the sizable favorite, but this could be a relatively tricky 1-8 matchup.
Upset probability: 28 percent
According to Vegas odds, the Pistons have 4-1 odds to upset the Cavs in the first round.
H/T to Mannie32 for sharing the link in the comments.