Coady, himself a centre-back who came through the youth ranks at Melwood, thinks the Netherlands international has been vital in turning Liverpool's fortunes around, improving the entire team.
The 26-year-old left Anfield five years ago, but he has loved watching Van Dijk take the Merseysiders to the next level.
"Everybody realises how good he is as a footballer, what he has done for Liverpool in the last couple of years and how he has approached the football club and improved the defence and the whole team," Coady told Liverpool’s official club website.
"The best thing about him is he is always in control of what he is doing, he is in control of an attacker, he is in control of how to defend a one-v-one.
"I remember when [Heung-min] Son was running at him in the Champions League final, you always knew he was in control of what he was doing and he ended up making a tackle in the end – which he has done for the majority of the season.
"The way he has changed Liverpool has been brilliant to see."
Van Dijk's solid performance in the Champions League final helped Liverpool forget the disappointment of losing out to Manchester City in a relentless Premier League title race.
Despite beating Wolves on the final day, Liverpool had to settle for second with 97 points - but Coady thinks Jurgen Klopp's side deserved the title.
"Anybody would tell you the same, not just Liverpool fans," he said.
"The way they did it and how they played, they deserved to win the league.
"To gather 97 points over a season is absolutely remarkable, they lost one game against Manchester City – which is ridiculous.
"I think that’s why everybody is happy that they won the Champions League, because they deserved something from the season.
"I just think City are an incredible football club – they are a fantastic team with brilliant footballers and a brilliant manager."