The 50-year-old has seen seven of his players called up for international duty just days before the club travel to Liverpool in their opening game of the Premier League season.
Speaking to BBC Newcastle, the former Birmingham manager called the friendlies "meaningless" and "ridiculous".
"I can't understand friendly internationals days before the start," he said. "Knowing our luck in games over the last year, plans may be laid to rest.
"I've never been a fan [of pre-season], I always despised it as a player."
Bruce took over at the Stadium of Light in 2009 after leaving former club Wigan Athletic.