Ex-WCW president Eric Bischoff says he was devastated by the death of pro wrestler Silver King -- telling TMZ Sports the guy was a legit trailblazer who never got the credit he deserved.

Silver King wrestled under the WCW banner back in the late '90s -- and Bischoff says the guy was a KEY reason for the success of the "WCW Monday Nitro" brand.

"The luchadores, that whole crew that came out of Mexico and were such a vital, important part of 'Nitro' ... they never really got the credit," Bischoff says.

Bischoff says Silver King and his crew "were really way more responsible for the success of 'Nitro' and giving 'Nitro' the ability to outperform [WWE] than they were ever given credit for ... including by me."

Silver King -- real name Cesar Barron -- died in the ring on Saturday during a luchador match in London. He was only 51.

Bischoff says he'll always remember Silver King for being one of the nicest guys in the business ... and also for helping to turn the luchador style of wrestling into the pop culture phenomenon it is today.

RIP