Forster, who has now played alongside van Dijk at both Celtic and Southampton, could come up against the defender as England meet Holland at Wembley on Tuesday night.
And the goalkeeper says he’s been impressed, but certainly not surprised, at the ease in which van Dijk has settled into life in the Barclays Premier League.
“He’s a massive player for us. The way he has come in and settled really quickly has been superb. He’s got great attributes – he’s big, strong and very quick,” Forster told saintsfc.co.uk.
“He’s fantastic on the ball and he’s been a great signing for us. I played a lot with him at Celtic and he was brilliant for us there.
“I can’t speak highly enough of Virgil. I think we’ve got a great understanding as a goalkeeper and defender.
“I almost know what Virgil is going to do before he gets the ball and does it himself, and that works the other way round as well, which is massive.”
And Forster believes van Dijk has already shown the rest of the division just how good he is since arriving from Celtic in the summer.
“I think he’s really show his qualities since he came down,” Forster added. “He’s shown the Premier League what he is all about, and has settled in so quickly.”