Frank defends Van de Ven after Slot slams 'reckless' foul on Isak
Defender Van de Ven crashed into Isak with a sliding tackle in a failed attempt to stop the Sweden striker scoring in Liverpool's 2-1 win at Tottenham on Saturday.
Isak, who limped off after Van de Ven's challenge, underwent surgery on an ankle injury that included a fibula fracture.
The 26-year-old is expected to be sidelined for at least two months after the injury to his left leg.
Slot launched a scathing attack on the centre-back when he faced the media on Tuesday, saying he was guilty of a "reckless challenge".
"If you make that tackle 10 times, I think 10 times there's a serious chance that a player gets a serious injury," he said.
But Frank defended his player in his own press conference.
"I am obviously disagreeing in many ways," he said. "We are talking about a defender that will do everything he can to avoid the goal.
"It is a transition, there is a ball down the side and he is doing everything he can to block the shot so he is sliding.
"Unfortunately, Isak plants his foot so it makes it look worse than it is, but that is a natural action for a defender.
"Put it this way, if my defender does not do that, they are not true defenders."
Frank said Van de Ven would not put an opponent's health at risk with a dangerous foul.
"Reckless challenge? I don't think you see anything like that from Micky," he said.
"I see him as a very fair and competitive player. That's one thing. I know the two players have sorted it out, so that's a good sign."
Tottenham's defeat against Liverpool added to the mounting pressure on Frank.
The former Brentford boss has struggled since arriving in north London in the close-season to replace the sacked Ange Postecoglou.
Postecoglou ended Tottenham's 17-year trophy drought by winning the Europa League, but the poor domestic form that haunted the Australian has continued under Frank's watch.
Tottenham are languishing in 14th place in the Premier League ahead of this weekend's trip to Crystal Palace, but Frank remains confident he can turn the tide.
"This is one of the biggest clubs in the world so it makes it a bigger and different challenge," he said.
"Where this makes it extra challenging is we also play Champions League and Premier League at the same time. We are trying to improve when at 100 miles per hour."