George Karl comes from the same "Larry Brown School" as Gregg Popovich, but that's about it when you compare their coaching styles.
Karl has coached his teams Nuggets teams the same way - a high scoring mentality that has them running and defending the paint as best as they can.
Gregg Popovich prefers a philosophy of playing to his team's advantages whether running or playing a set offense (or a mixture of the two depending on who's on the floor). The one thing they do have in common is their coaching philosophy and Karl admits it to the Denver Post:
"I think I'm a Spur guy — I think solid and fundamental win more than spectacular,"
Don't let Karl's teams fool you. They may be trying to play a high octane offense but, unlike the Phoenix Suns of old, you're not going to get flashy egos showing up on his watch.
JaVale McGee may be an "interesting" personality, but Karl has molded him from "flashy" to "efficient" in his defensive game and you won't see him taunting opponents by doing push ups like Amar'e Stoudemire years ago.
Like Popovich, they share a philosophy of treating the game like a job that you have fun doing over just having fun on the court. They both share the philosophy that "Sports Center" type plays on a daily basis don't get you a championship and that's a major goal for their ownership and more importantly their fan (as Spurs fans will tell you their disappointment of the postseason in recent years).
Karl is the guy who seemed to tame Allen Iverson's ego during his brief Nuggets run, so you know where his loyalty to the game is. He prefers the "boring fundamentals" over the flashy Top 10 plays.
It's hard to argue with Karl on his own description. He is as close of being a "Spur Guy" as you can get without being on the Spurs.