In Furious George, the 65-year-old alleged the NBA has a widespread problem with illegal substances, per Dan Feldman of NBC Sports:
I'm talking about performance-enhancing drugs—like steroids, human growth hormone, and so on. It's obvious some of our players are doping. How are some guys getting older—yet thinner and fitter? How are they recovering from injuries so fast? Why the hell are they going to Germany in the off-season? I doubt it’s for the sauerkraut.
More likely it's for the newest, hard-to-detect blood boosters and PEDs they have in Europe.
While noting the NBA has tougher drug testing than the NFL and MLB, Karl also said the league is often steps behind the "cheaters."
Karl never coached Bryant or Wade, however, so he may not have intimate knowledge of the treatment in Germany or its legitimacy.
Some players Karl did coach were already upset with him. Another passage in his book ripped New York Knicks star Carmelo Anthony, Cleveland Cavaliers guard J.R. Smith and retired big man Kenyon Martin, who all played under Karl during his time with the Denver Nuggets.
Per Marc Berman of the New York Post, Karl called Anthony a "conundrum" who was a "user of people" and "addicted to the spotlight."
Martin was quick to respond to the criticism:
Karl has spent 27 years as a head coach in the NBA with six different organizations. He was most recently the coach of the Sacramento Kings, who fired him following the 2015-16 campaign after accumulating a 33-49 record.