I am not big on PER and Sabermetrics, I prefer to just use my eyes, but I do know that it is very difficult to have a -0.7 PER, which according to ESPN, is the worst in the history of the NBA Playoffs.
In case you were wondering PER stands for Player Efficiency Rating. It was created by ESPN John Hollinger, who ironically works for the Grizzlies now. Here is how he defines it.
The player efficiency rating (PER) is a rating of a player’s per-minute productivity.
To generate PER, I created formulas — outlined in tortuous detail in my book “Pro Basketball Forecast” — that return a value for each of a player’s accomplishments. That includes positive accomplishments such as field goals, free throws, 3-pointers, assists, rebounds, blocks and steals, and negative ones such as missed shots, turnovers and personal fouls.
I can break it down a little simpler for you. Kendrick Perkins just wasn’t very good in the playoffs.