Former U.S. assistant coach Andi Herzog says Major League Soccer had no interest in listening to advice from Jurgen Klinsmann when he was in charge of the national team, saying league officials "thought he was just criticizing everything."

Klinsmann, who was fired in November after two World Cup qualifying defeats, endured a frosty relationship with the MLS leadership during his five years as United States coach.

He said in 2014 that U.S. players like Clint Dempsey and Michael Bradley would have to prove their form hadn't dropped after leaving Europe to return to North America. In response, MLS commissioner Don Garber called Klinsmann's comments "detrimental" and "personally infuriating."

Months later, Garber said MLS would continue to pursue top American players "regardless of what our national team coach might want to do," prompting a slight rebuke from U.S. Soccer president Sunil Gulati. Garber later said it was "unfair and unwarranted" that Klinsmann left so many top MLS players out of the national team in favor of European-based players.

Herzog, Klinsmann's top assistant, told ESPN FC that the bad blood stemmed from MLS leadership being resistant to any suggestions Klinsmann might have had on the league.

"MLS, the American league, is getting better and better, but Jurgen wanted to help them and give them some information, some inputs, where they were making some mistakes," Herzog said.

"Jurgen said, 'Yeah, we need to do this, this and this better,' and this was the reason why he started to have a fall-out with the [commissioner] of the league, Don Garber.

"Jurgen wanted to help the league keep improving but [MLS executives] were not happy and thought he was just criticizing everything. One point Jurgen was not happy with was that they were buying and overpaying over-aged former European superstars like crazy, but they have already found out that it is not a good way.

"And this was a big problem, because there was a big pressure from [Garber]. ... When we lost a game, [Garber] came and said: 'No, he's criticizing our league and he's making some mistakes, too.' So this was a problem -- a bad relationship between the American league and Jurgen.

MLS declined to respond to Herzog's comments.

Andi Herzog was an assistant to former United States coach Jurgen Klinsmann. Shaun Clark/Getty Images

Despite Klinsmann's sacking, Herzog is not bitter about the way things ended and said he enjoyed his time with U.S. Soccer.

"To be honest, it was big fun. In five years, it was such as great and nice experience," Herzog said. "OK, they fired us but I was not really angry about anyone. They gave me so much new challenges, experience, and it was so great to be there."

Klinsmann's reign ended after defeats to Costa Rica and Mexico, damaging the U.S.' hopes of qualifying for the 2018 World Cup. That came after a disappointing fourth-placed finish in the 2015 CONCACAF Gold Cup, and a loss to Mexico in a playoff for the Confederations Cup.

The U.S. and Mexico have long dominated CONCACAF, winning all but one of the Gold Cups and qualifying for every World Cup since 1994. Herzog said he believes the region is not as easy to compete in as it might seem from outside North America, Central America and the Caribbean.

"When you are in Europe, you don't know CONCACAF," he said. "There was Costa Rica, and they made it to the quarterfinals of the World Cup, where they lost to Netherlands after penalties. This is already a good team.

"Then, you play against Honduras. When you are playing there, there are 40 degrees [Celsius, or 104 Fahrenheit], the grass is six or 10 centimetres longer than normal, they play in the heat at 3 o'clock -- we did not play at 8 or 9 in the night, but at 3, when the weather was the worst.

"It was February and our players came from England, Germany, where they were used to having rain or snow, and then they played in 39 degrees. So they tied after 60 minutes and then they lost to Honduras. And that's normal, because, in CONCACAF, every team has something special.

"Even the quality of USA and Mexico should be better, but in Mexico, you play in altitude, there are aerial differences, you cannot sleep the whole night because the people are crazy in front of the hotel, making so much noise. That's completely different to Europe, but it was still a new experience and adventure."

Former U.S. assistant Andi Herzog says playing in CONCACAF is much harder than it might appear. RODRIGO ARANGUA/AFP/Getty Images

Before he was fired, Klinsmann had been linked to taking over his former club Tottenham Hotspur, as well as the England national team, and Herzog said it won't be long before Klinsmann is coaching again.

"I think he will be back, the question is if he wants to take over a club team or another national team," Herzog said. "That's his decision, but I think sooner or later, because of his name, and we also had some success with U.S. team, he will.

"So, I'm sure there will be some new [interested] teams, maybe a Premier League team or another national side. We will see."

As for Herzog. he's also looking for an opportunity to return to coaching soon, but now as a head coach. He was previously linked to taking over Werder Bremen, the club where he spent the peak of his playing career.

"After they fired us from the U.S., I wanted to spend another two or three months with my family, and now I am open to something new," he said. "There was something going on right after they fired us but at that time I said I needed a little time for a break to get into a better mental position after those difficult five years.

"Right now I am really relaxed, everything is fine and I am waiting for the next possibility to start as a coach again."

Lukas Vrablik contributed to this report for ESPN FC.