Laker Nation better prepare for the worst ... 'cause NBA super fan Jimmy Goldstein says L.A. has a snowball's chance in hell to beat the Memphis Grizzlies in the first round of the playoffs -- telling TMZ Sports it would be a complete shock if LeBron James and Co. won the series.
Goldstein holds the record for attending the most NBA games in the history of the league ... so naturally, he was present for the Lakers' play-in game against the Minnesota Timberwolves on Tuesday.
Jimmy G says he was thoroughly unimpressed with what he saw from the Purple and Gold in the overtime thriller .