Barca now have six centre-backs in their squad and only three - Gerard Pique, Samuel Umtiti and new signing Clement Lenglet - appear guaranteed to be at the club when the season begins.
Over weeks, a deal with Tottenham for Alderweireld had stalled and that's where many other names came to the fore.
The trio looked to be ready to leave Spurs since January, with Dembele and Alderweireld not getting any closer to signing new contracts with Mauricio Pochettino's side.
Alderweireld went to the 2018 World Cup with Belgium and started all but one game as the Red Devils finished third in Russian Federation.
It is believed Spurs will look to the likes of Lewis Cook at Bournemouth to replace Dembele, with Pochettino's penchant for developing young talent flawless for these kind of situations as he looks to move on veteran stars.More news: Facebook shuts down accounts for inciting political, social tension
However, The Sun are reporting that Mina's agent, Felipe Russo, has scuppered the proposed move to United by altering the terms of the deal.
The 23-year-old shone for Colombia at the 2018 World Cup, scoring twice with powerful headers as he first got them out of the group stage and then took their Round of 16 clash against England to extra time.
Spurs were adamant in asking £75m for the defender, but United weren't keen to shell out as much.
We reported earlier this week that United could seal a deal for Mina for as little as £30m, just seven months after Barca signed him from Brazilian club Palmeiras for £10m.
It, however, remains to be seen who he will line up within United's defence, with Eric Bailly, Chris Smalling and Phil Jones still among Mourinho's options.