Spurs beat Southampton to his signature in the summer after he spent last year on loan at the Saints, and his addition has been of real benefit to the club's backline.
Alderweireld is playing alongside Belgian international teammate Jan Vertonghen, also his former Ajax teammate, with their partnership rendering fellow new boy Kevin Wimmer very much a forgotten man.
Asked to pick his top five players of the season so far, Redknapp named Jamie Vardy, Dmitri Payet, Santi Cazorla, and Anthony Martial, along with the Tottenham star.
He said of Alderweireld: "Best defender in the league this season. Jan Vertonghen has benefited from playing with him."
The statistics to back up Alderweireld's impact are telling. Tottenham have seven fewer goals conceded after 12 games of the 2015/16 season with him, as opposed to the first dozen of 2014/15 without him.
Meanwhile Southampton's defence has had the opposite effect, going from one of the meanest in the league, the middle of the pack in Alderweireld's absence.
Alderweireld and Tottenham will be disappointed their defence could not close out the game at the weekend, giving a number of opportunities to the Gunners to get back into the game, but the Belgian's overall impact cannot be denied early on this season.
Manchester United's Chris Smalling has been putting together his own case as the league's best defender this season, certainly he is the most improved, while Winston Reid of West Ham has also been particularly impressive when fit.