The 25-year-old has arguably been one of the Black Cats' best performers this season.
The former Chelsea player has been hugely impressive going forward, but had previously come in for criticism due to his defensive work. But Allardyce explained how after working with the 25-year-old on the job he is predominantly in the side to do, he has become an even more important player to the team's cause.
"I've enjoyed working with a talent as big as his and trying to enhance it into being one of the most consistent full-backs in the league," he told the Shields Gazette.
"From my point of view, it was just about telling him to defend like this and this.
"Going forwards, it's his forte and he can make and score goals."
With the battle at the bottom of the table setting up to go right down to the wire, the Black Cats boss will know that it may come down to the fine margins to decide who will be playing in the Championship next term.
And one of those fine margins could well be which defence makes the fewest mistakes during the final weeks of the campaign.
With four of their remaining fixtures coming against sides in the top half of the table - including home games against title-chasing Leicester and Arsenal as well as champions Chelsea - van Aanholt's main role for the majority of the remaining games will be to ensure that things stay tight at the back.
And if the Dutchman can put in a defensive display that helps the club stay up, and perhaps still manages to add to his three goals and two assists in the league, then maybe more people will agree with Allardyce's assessment of the full-back's ability.