If vad was manager of Spurs and I was manager of MUFC, I would offer him Rojo for Vertongen straight up. And I'd snicker when he accepted.
They play different roles - Rojo is definitely the athletic enforcer type and Vertonghen is the more cultured ball playing type - so it'd be hard to swap them for each other, but I do rate Rojo quite highly and think as he's matured (he's still quite young for a center half) that he's turned into a damn good player back there.
I also have to watch Vertonghen's flaws on a weekly basis so I'm likely more frustrated by what he does wrong than I should be. He's surprisingly awkward for someone who moves the ball the way he does, and he gets done far too easily by tricky / quick attackers - guys like Aguero or Mane just eat him alive and one of the huge benefits of going to 3 at the back for Spurs is that Vertonghen much more rarely gets isolated against players like that. It's also one reason Spurs have struggled so badly with Liverpool in the Klopp era, Vertonghen has nobody to really mark and ends up getting his feet tied up trying to step and chase Firmino/Coutinho/Mane, etc.
That being said, he's magnificent as a LCB in a back 3. He has cover against pacey attackers defensively and in possession teams have to choose to make either him or Dier the free man at the back and both pass the ball like midfielders. He's a good player in a back 4 if he has a very mobile partner, but he's a great player in a back 3.
I'd be tempted to trade Kane before Toby, though that'd be like choosing which child to sacrifice. The Vertonghen led defense of 2014-2015 shipped 53 goals. Alderweireld showed up and it immediately dropped to 35 and will be even lower this season. Alderweireld is the best center defender in the PL by a chasm the size of the grand canyon - he is so mobile, reads the game so well and keeps the rest of the defense so organized that any match he misses the entire structure looks wobbly. He's the glue that holds that entire group together, and without him Spurs are at best an average defensive team (see: Champions League where Alderweireld started only 2 of 6 matches and Spurs leaked stupid goals all over the place).
Nobody thought a defense made up of Vertonghen, Walker and Rose would be anything other than questionable defensively (and questionable is a kind way to describe how that group hemorrhaged goals over a several year period). All of them are attacking minding players for their positions. Add Toby! and you suddenly have a fucking fortress. He has the same effect for Spurs that Vincent Kompany has for Manchester City, transforming the team just by being on the pitch.
That's also why the fact that Toby! is the only Spurs player to not sign an extension recently scares me. He's irreplaceable for Spurs.
