There were many dismayed United supporters on Sunday as the Reds fell to Newcastle at Saint James' Park, none more so than former United defender Phil Neville.
The Manchester club were not firing on all cylinders Sunday lunchtime and could have lost by more had had a good penalty shout been given against them or if Antonio Valencia had seen red for a reckless high boot.
Appearing on MOTD2, the recently appointed head coach of the England Women's team, didn't hold back in his assessment of the pairs' recent performance:
They've (United) got the best defensive record because they've got the best goalkeeper in the world, they've got Matic sat in front that protects them really well, but the last two games ... Smalling and Jones had a disaster.
Against Dele Alli and Harry Kane they got bullied. Today, did they make many mistakes? No. They created a nervousness and a tension and they were making decisions that were strange.
Neville went on to reason that the England pair are no longer 'potential' players, that they fail to take responsibility and that it might be best for Mourinho and United if they don't play together:
They were bought these two as the best young centre backs in England. The thing that I noticed today is that they didn't take responsibility on the ball, they were sloppy on the ball.
The point about Jones and Smalling now, it's not about potential, they're experienced now and I just wonder whether as a partnership if José has to split them up and put Rojo with one of them or Lindelof with one of them but playing them together, particularly in the away games i think has created a nervousness around the team.
Does Neville have a point or are the pair just going through a bad patch? United have kept 15 clean sheets this term and Jones and Smalling have played 19 and 21 times in the Premier League this season, so they obviously have to take some credit for United's defensive resolve.
But, perhaps Neville is right and the two England centre halves just can't gel together as an effective partnership, and if so, it surely spells an exit for at least one.