Only two years left on Dieng’s contract at $16.2-$17.2 per year, so would be okay adding him. If he had 3-4 years left then no way. On/off numbers aren’t great on him, but that’s also a result of him not playing with Towns. He’s a good backup center, albeit expensive.
Covington is who he is offensively - a passable offensive wing that can spot up and score without killing your lineup. Minnesota has been significantly better defensively with him on the floor and numbers prove it out. There’s real value in that, especially if the Spurs could tick up that 3pt percentage.
Bigger question is why would Minnesota want to pair Aldridge with Towns?
I’d consider the trade depending on what first rounder we were talking about. Aldridge is aging but still is an All NBA caliber player (regardless of if he makes it or is one of the first guys out).