Klinsmann questioned his players' work ethic earlier this month during their annual pre-MLS season training camp, which included friendlies against Chile and Panama, claiming they were not fit enough to run out games.
Sporting defender Matt Besler did not criticise Klinsmann on Friday but did insist he was comfortable with his fitness three weeks before the 2015 MLS season.
Vermes - Besler's coach at Sporting - was much more critical.
"To expect those guys to be in top form in a January camp is - and I mean this - utterly ridiculous," Vermes said at a media conference on Friday.
Klinsmann had argued his players should have used part of their time off - the regular season of the MLS finished at the end of October, while the play-offs were completed in early December - to improve their fitness before the USA's training camp.
"Totally disagree with the comment," Vermes said.
"You know, I have a lot of respect for Jurgen. Obviously, he was a great player. He's done tremendous things as a coach as well.
"But that doesn't mean every time somebody opens their mouth that they're right."
It is not the first time Klinsmann's take on the MLS has sparked controversy with the German having questioned Clint Dempsey and Michael Bradley's decisions to return home from the Premier League and Serie A, respectively, in 2014, which prompted a tongue-lashing from league boss Don Garber.
According to Vermes, Klinsmann has yet to grasp the unique nature of football in the USA compared with the European leagues.
"[My argument] comes from taking in how big our country is, and our league, and the amount of travel that goes with it, and the environment that we play in," Sporting's boss said.
"If you're a European player, you're playing through all the colder weather months, as opposed to the hot-weather months, like we do here. That takes a toll."
Besler claimed Klinsmann's claim may have been based on skewed data with the USA's collective fitness being compared with how they were tracking just before the 2014 World Cup.
The 28-year-old defender made it clear he was not worried about Klinsmann's comments.
"He [Klinsmann] can say whatever he wants. But from my perspective, my goal is to be at my peak fitness on March 1," Besler said.
"That's when my season starts. It goes from March to December. So on January 15, we devised an off-season plan for me to hit my peak fitness on March 1. I think that's what most of the guys did.
"So if the expectation was different, that's something that needs to be discussed, so we know going into a camp where we need to be. But honestly, I think he just likes to push his players."
