Virgil van Dijk feels former Celtic team-mate Kieran Tierney should be in no rush to leave Parkhead as his remarkable progress continues.
The 20-year-old defender reached another milestone in his young career when he captained Scotland in a 1-0 friendly defeat against Van Dijk's Holland side on Thursday night.
Tierney has also worn the armband for Celtic and is closing in on a 100th first-team appearance for his boyhood heroes after signing a new long-term contract last week.
Van Dijk was playing when Tierney came on for his debut at Dens Park in April 2015 and the Southampton defender has watched his former team-mate's career take off since then.
"He's been doing very well and I think Celtic are very smart to tie him down for the next six years," the Dutchman said. "It's good to see him as the captain as well.
"I can remember that day he made his debut at Dundee. Since then he has been progressing every game."
Van Dijk refused to speculate on how far the left-back – who impressed in central defence against Holland – can go in the game.
"That's not up to me but it's good to see he's making progress," he said. "He was the captain of his country and that's very special at 20 years old.
"I don't even know if he wants to go to the Premier League. Celtic is an amazing club for him as well and I don't think there is any rush for him to leave."
Tierney has been a key part of Celtic's 63-match unbeaten run in Scottish football and van Dijk believes their achievement has been under-rated by some pundits.
The likes of former Celtic striker Tony Cascarino has downplayed their run on the account of his perception of the standard of Scottish football but van Dijk labelled that unfair.
The 26-year-old overcame similar scepticism over his own performances for Celtic before moving to Southampton and establishing himself as one of the best defenders in the Premier League.
On Celtic's run, he said: "It's amazing and I don't think people really understand how big an achievement it is. They should get all the credit for it becaue it's not something that happens a lot.
"I'm happy for the club and the fans, and also for the players of course.
"It doesn't matter if it's Scotland or anywhere else, it's an amazing achievement and people don't really understand how big it is."